Imagine the scene. You’re a middle-aged woman, sitting around the table with your husband, your mother and your teenage daughter. Your husband is saying how hard he tried to give you the best 40th birthday party ever, and you didn’t even appreciate it. Then you announce that you never wanted to get married in the first place because marriage is a trap, but your mother forced you into it because you were pregnant. Grandma responds that this is news to her, but agrees that your wedding was horrible. Your daughter is just staring at all of you and saying wow a lot.

Well, you don’t actually have to imagine it, because this is a real conversation that Hollywood stars Jada Pinkett Smith and her husband Will Smith had at home in Calabasas, California, with their daughter Willow and Jada’s mother Adrienne.

They weren’t alone: the conversation was recorded on camera as an episode of Jada’s series, Red Table Talk, an online discussion show which is broadcast on Facebook Watch and which has become the breakthrough unscripted hit in the world of social-media television.

But why, why would they reveal all of their deepest darkest feelings in public, for total strangers to gawp at? How can they all recover from each other’s revelations to make another episode the next week? Didn’t the Smiths used to be a really private family? Didn’t we all used to be?

Tales from the table: three generation of Jada Pinkett Smith’s family get down to business as they discuss controversial topics in Red Table Talk on Facebook Watch. Photograph: Stan Evans

Jada Pinkett Smith, who is now 47, sits in a meeting room at the Facebook headquarters in London, a skyscraper made of glass that overlooks the whole of London, and with her hair in a shining gold wrap, her voice slow and steady and utterly dignified, she explains it to me.

“When I was going through a really tough time in my life,” she says, with her publicist sitting beside her, silently, “there were three women, three friends, who were so honest with me – I mean so honest with me, saying some stuff you would never expect anyone to say – that they re-directed my journey. But it wasn’t necessarily advice, it was that they were willing to spend time with me and share. Before that… well, usually we women have to tell our stories in a safe way, because people often want to persecute us for being sexually free.”

The three women were all married and all actors: Salma Hayek, Pauletta Washington (married to Denzel) and Ruby Dee, and these conversations about marriage and relationships, with which she was really struggling, led Pinkett Smith to believe that there was room for such intimate chats to take place on a bigger stage. An actor herself – she had been a star in the 1990s, starting out on the Cosby spinoff-series A Different World, co-starring in The Nutty Professor with Eddie Murphy, and later in the Matrix franchise – Pinkett Smith had spent many years feeling frustrated by her position as wife to the more successful husband. She says: “I forgot who Jada was.” She put her family’s needs first and forgot her own, while Will roamed the world, a megastar applauded by millions. They didn’t exactly break up, but during the bad patch she moved to New York on her own for a while, to find herself.

They first met when they were barely adults; he was starring in The Fresh Prince of Bel Air and she was on A Different World. They later married and had two children, Jaden and Willow. “I knew that I was not built for conventional marriage,” she explains. “Even the word ‘wife’: it’s a golden cage, swallow the key. Even before I was married, I was like, ‘That’ll kill me.’ And it damn near did! So why wouldn’t you share what you’ve been through, when you see that other people are out there, trying to figure this crap out? We decided to make it public because it’s part of the healing. I feel like if we don’t have real understanding about it, I don’t know if interpersonal relationships are possible.”

Jada wears roll-neck by versace.com ; body suit worn underneath by nubianskin.com

They clearly dote on their children, and she stresses the strength of their union, too. “Will is my life partner and I could not ask for a better one. I adore him, I never want people to think it was Will I didn’t want to marry – he and I were talking about this the other day. But I can assure you that some of the most powerful women in the world feel caged and tied, because of the sacrifices they have to make to be in that position. So I wanted to talk about how we really feel about marriage. How do we really feel about different, unconventional relationships? How do we really feel about raising children? Honestly.”

Which is why, in Red Table Talk, you will hear some really quite startling conversations. The first one involves Jada sitting down to talk to Will’s first wife, Sheree, mother of his eldest child, Trey. When the two of them discuss how hard it was to find a way to co-parent at the start, with the children going between the two houses, and how Jada hadn’t realised that she was marrying someone whose first marriage wasn’t really over, you can hear a pin drop. Sheree recalls a time when she called Jada’s house to speak to her son, and Jada didn’t like her tone, so she put the phone down on her. Ouch. Yet the conversation clearly liberates the two of them from some very old feelings. Jada tells me that it brought them closer together; Will has said that there is some “transformational magic that occurs when people sit down at the Red Table”.

The usual set-up is this: Jada, Willow and Adrienne sit round the table, usually accompanied by a guest, such as Kristin Davis, who played Charlotte in Sex and the City and who came on to discuss why she adopted a black child as a white woman, and to hear what feelings this can stir up in black women. Or Jordyn Woods, vilified by the Kardashians for her involvement with the father of one of their children, who came on to explain what really happened, and how her life has since been torn apart by public crucifixion via social media. Key to it, though, is the inter-generational axis of mother, grandmother and daughter, who manage to discuss their thoughts on porn, threesomes and love with a level of dignity that I tell Jada astonishes me – I think I’d die from squirming before having those conversations with my own family.

Jada wears white dress by brunellocucinelli.com ; belt with gold detail by bottegaveneta.com ; and earrings by shaunleane.com

Jada will reveal, for example, that she spent several years addicted to porn and felt it had to stop when she was climaxing five separate times a day. Her mother will nod. Yet she tells me she was actually deeply uncomfortable. “I think the pornography show was the first time I got squeamish talking with my mother. Not so much Willow, because we had already talked about it.” Willow had shown her mum her Tumblr feed (a collection of blogs that she followed online) when she was about 11, only for deeply unsuitable material to flash up that Willow, now 18, insisted had nothing to do with her. “So she’s flippin’, flippin’, flippin’ and some of the most hardcore pornography came up and I was just like – ‘What the hell is this?’ So the first time I had to talk to her about it was then. She was so used to it, she couldn’t understand why I was trippin’ about it. So then I had to go, ‘When was the first time you saw it? How did it make you feel? You have to know that this is not lovemaking, right?’” Then she laughs. “I also told her, you know what I had to go through to get some porn!” It was her older brothers who had first shown her it, “and older siblings expose younger siblings to everything. I think every kid today is introduced to sex through porn.”

Which is why there is such a need for these frank, urgent conversations. A community has built up around the show on Facebook, with thousands of users discussing their own lives in the comments section. Pinkett Smith admits to me that she has a fake Facebook identity she uses to log in and encourage them, something I find hysterically funny, though she assures me she doesn’t log in to say how great Jada Pinkett Smith is. One of the reasons she decided to take this show to social media, rather than mainstream television, is that after a round of pitching meetings, Pinkett Smith felt that only the Silicon Valley giant was offering true flexibility with the content. “The others all wanted to add a dancing bear to it. So many dancing bears, when I just wanted us sitting around a table. And the other reason I couldn’t go to mainstream TV is that Willow is not built for that kind of conventional set-up. She can’t be there every episode – she’s a little butterfly. Something comes up and she says, ‘Ma I got to go to the mountains for a week,’ and I got to let her go. That’s part of her mental health, she needs freedom. You’ve just got to let her fly.” Her brother Jaden, 21, has appeared, but is generally “too busy, he’s busier than any of us, he can’t sit still for more than a day,” with his music, not to mention his new career as a tech inventor. (He has described himself as “obsessed with water” and has created a new filtration system to help the people of Flint, Michigan, who have lived without access to an uncontaminated supply for years.)

We learn, through Red Table Talk, that when Willow became a child star with her hit single, Whip My Hair, when she was nine, she soon went off the idea, but couldn’t get her father to hear her pleas. Will admits he was so determined to turn her into a star, the youngest artist to sign to his friend Jay-Z’s label, that he wouldn’t let her stop touring. Willow and Jaden ended up giving a joint interview to the New York Times, after which the internet had a good laugh about their cosmic musings on the nature of reality. I ask Jada how she feels about it all now.

“It was a very tough period,” she admits. “They had to grow up really fast. But, you know, we all have our crosses to bear and I’d rather have to deal with Twitter trolls than be these mothers on the streets of Baltimore worrying about gun violence and getting my kids home safe.”

Three of the best: Jada Pinkett Smith with her daughter Willow and mother Adrienne on Red Table Talk. Photograph: Stan Evans

It is not a comparison she makes flippantly; it is the life she could have lived, having been raised there herself, her single mother Adrienne giving birth to her while still at high school in Baltimore, before she (Adrienne) became a heroin addict for 20 years. Pinkett Smith, whose own children have grown up with a swimming pool, an in-house vegan chef and been privately educated alongside the Kardashians, admits she sometimes struggles “to relate to my children’s problems, because of how they have grown up. Survival is not an issue, so what is?”

Her love for them is palpable; so is the pain in her face when she admits she doesn’t really understand her own problems either. “When I think about my life experience and equate it to the amount of pain that I feel – it doesn’t match, it doesn’t add up.” She adds that “trauma is a plague,” and that the African-American experience carries the burden of generational traumas, “on top of present times”.

Yet she clearly suffered a lot: her mother is known in the family as “Gammy” and is such a cheeky, grinning, calm presence on the show it is still surprising when she talks about her junkie years. Jada says they are exactly why her mother, to whom the show has brought her closer, is so good at being on it; so able to sit through uncomfortable conversations. “Being a recovering addict, she’s had to do a lot of self-evaluation, even outside of the therapy. She’s gone beyond, ‘Ugh, I feel so ashamed’ into: ‘It is what it is,’ and she has a lot of resolve about what it means to be the child of addicts. She also knows my healing is my responsibility and that it’s up to me to handle my co-dependent issues, because I’m deeply co-dependent.”

With her? With Will?

“With everybody! It’s what got me into the dynamic of the relationship I have with Will. You know, you start off thinking, ‘It’s his fault, if he hadn’t…’ No, no, no – nobody put a gun to your head, Missy. What was your responsibility in this? Cos your ass is co-dependent, that’s what.”

‘If we don’t have real understanding about it, I don’t know if interpersonal relationships are possible’: Jada with her family (from left) Trey, Jaden, Willow and Will Smith. Photograph: Randy Shropshire/Getty Images

I ask what Will thinks of the show. “He loves it! He thinks I’ve finally, really found a place for my voice.” She is also acting again, and has a new movie coming out this month, Angel Has Fallen, a terrorist thriller with Gerard Butler and Morgan Freeman.

Oh and – one more thing – that rumour about you being a Scientologist? “Oh I know everybody keeps wanting to make me into one, but I’m not. If I were, I would have no problem saying it.” She says she has studied many religions, including taking a few classes in Scientology, and has a library at home full of books about all faiths, but has opted for none of them. She attributes this to being partly raised by her own grandmother “who was a remarkable West Indian woman, from Jamaica, and very spiritual, but she did not believe in organised religion. She took us to the Ethical Society of Philadelphia.” The organisation championed a free-thinking humanism. “Can you imagine, a black family that didn’t go to church?” Jada cackles with joy at the memory of her unconventional grandmother. “She told us: ‘You choose your God’ – so I don’t have one.”

Later that night, Pinkett Smith will appear on stage at an event in London, interviewed by the BBC presenter Clara Amfo, who will ask her about possible future guests on her show. “Meghan Markle’s got to call me!” Pinkett Smith will laugh, to huge cheers from the audience. “But only when she’s got a story to tell.”

Makeup by Liz Pugh at Premier Hair and Makeup using Westman Atelier Lit Up Highlighter Stick, £44, and Baby Cheeks Blush stick in Dou Dou, £46, both net-a-porter.com; hair by Ben Talbott at the Wall Group using Color Wow; photographer’s assistant Liam Bundy; digital by Andrew Mayfield; fashion assistant Peter Bevan.

New episodes of Red Table Talk will be available exclusively on Facebook Watch in September