The Democratic presidential candidate is more than you might expect

First thing through the door, little Dylan Driscoll, 4, demands to know one thing from his grandfather, the presidential candidate Bernie Sanders: “Are we going to play Monster?”

At Grandpa Bernie’s house in Burlington, Vermont, “Monster” is the latest thing – and, soon enough, the senator who wants to be president is growling and chasing after Dylan and his sister, Ella, 7, while they giggle and shriek.

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There goes The Washington Post‘s portrait of Sanders as “Grumpy Grandpa.”

“Anybody who knows him knows that isn’t true,” the senator’s wife, Jane O’Meara Sanders tells PEOPLE in an at-home interview for this week’s issue. “Sometimes he is grumpy with reporters when they’re not covering the important issues, but not with us.”

She said her other grandson Cole, 11, is “the one who’s bothered most” by the bad press. “Cole will complain, ‘They said he’s a grumpy grandpa. He is not! He’s a fun grandpa.”

And his home is littered with evidence: the kiddie electronic keyboard tucked beneath the kitchen counter, the pink plastic play kitchen crowding the doorway to the foyer, the swing set, baseball bats and wiffle balls on the back lawn.

What else did PEOPLE learn about Sanders when we spent the day at home with him and his family recently?

No One’s Ever Called Him ‘Dad’

B, the Bernster, Bernard, Bernie, Grandpa Bernie, Grandpa Bern.

Take your pick, but the only familial name Sanders has never been called is “Dad.”

Jane’s three children from her first marriage – Heather Titus, Carina Driscoll and Dave Driscoll – first knew Sanders as “Bernie” during the eight long years he dated their mom. So, once the couple married, “Bernie” stuck.

And Sanders’ only biological child (with a former girlfriend), Levi Sanders, grew up saying everything but “Dad.”

“When I was a little kid, I started with B. Then it was Ber and then Bern and now it’s Bernard. Or the Bernster. I’ve never called him Bernie. And I never have called him Dad,” says Levi. “Even when I was six years old, I thought it was childish. He was a friend, not an authoritarian.”

For more of our at-home interview with Senator Sanders and his family, pick up the new issue of PEOPLE, on newsstands now

He’s Jewish and has played Santa

In the Sanders home in December there was a grand Christmas tree, lawn decorations outside and Christmas knickknacks on the bookshelves – all from the O’Meara side of Sanders’ blended family, says Jane.

“Christmas was always a huge thing for us, so Bernie learned how to do that,” she says. He even dressed up as Santa when he was mayor of Burlington in the 1980s to give out presents to families in low-income housing.

As for the Jewish holidays on the Sanders side of the family, step-daughter Carina Driscoll remembers Sanders always being very private about his religion.

“Bernie would observe his traditions in a way that we really didn’t see very much of. The matzo crackers and gefilte fish would come out and we’d be like, ‘Uh-huh. So that’s happening.”

Says Sanders: “Spirituality is something I think people should hold generally hold to themselves so it s not something that I talk about a whole lot. But I m proud to be Jewish and being Jewish is a very important part of my life.”

He was 25 years late with an engagement ring

After proposing marriage in a Friendly’s restaurant parking lot, Sanders didn’t cough up a diamond ring until his and Jane’s 25th wedding anniversary, she says.

Describing the belated engagement ring as the best present she ever got, Jane says, “He just surprised me and said, ‘Let’s go shopping for it.'”

Apparently shopping is not her husband’s strong suit. After they started dating in 1981, Jane admits that she would “pre-shop” for gift possibilities with a friend who worked at the local JC Penney. (Husbands of the world, take note.) “She said, Look, why don’t you just come in and show me what you like so that I can point him to something?'”

He’s a little bit country, a little bit classic

A good car stereo – American-made – is Sanders’ only real splurge, his family says. And what does he like to listen to on it?

“I listen to all kinds of things. I like Motown sounds. I like country music, classical – Beethoven, you know, those guys. Willie Nelson, Merle Haggard.”

And is Killer Mike, the rapper who is campaigning for Sanders, on the playlist?