The man who ran the illegal “Ghost Ship” artist enclave in Oakland — where at least 36 people died in a fire on Friday night — was a deadbeat dad who neglected his kids to hold drug-fueled sex parties inside the warehouse, according to family and friends.

A pair of caregivers for Derick Ion Almena’s three children told the Daily Mail that the free-spirited 46-year-old would often leave the youngsters with them for up to five days at a time while he got strung out with his wife, Micah Allison, and gallivanted in Bali and other places.

“They were crazy. I remember having conversations with Micah. She would say, ‘Oh, we danced under the moon, it was this transcendent experience,'” recalled Mariah Benavides, who was just 16 years old when she started watching Almena’s three kids, who now are ages 14, 8 and 5.

“I wouldn’t say they’d disappear without contact. They’d say, ‘We’re going to go and have fun’ and they were going to be gone a bit longer,” Benavides added.

Danielle Boudreaux, a longtime friend of the couple who was also looking after the kids, told the Daily Mail and the Associated Press that Almena and Allison had been raising them like animals.

“It went on for a certain amount of time with me constantly picking the kids up from school, bringing them home to my place, bathing them, feeding them,” Boudreaux remembered. “They all had lice repeatedly. I was picking lice out of their hair. They’d missed 50 days of the first 100 days of school.

“I was confronting him on a regular basis,” she said, noting how “meth was the primary drug of choice” for people who hung out at Ghost Ship.

“I grew up among drug addicts, I knew what was going on,” Boudreaux said. “I have a hard time with people saying they were just doing art.”

According to Benavides, at least seven or eight people who lived at Ghost Ship were staying downstairs and “had trailers like RVs in the building.”

“It was a terrifying place for children, it was a terrifying place for me and I was 18 at the time,” she said.

Just hours after the fire erupted inside his 10,000-square-foot warehouse, where a party was being held Friday, Almena sparked widespread outrage by penning a Facebook post in which he griped about losing everything he “worked so hard for” — without noting the tragic loss of life.

Countless social media users felt he ultimately had no right to say anything about the blaze, especially since his building was the subject a city code enforcement probe at the time, with officials citing complaints about health and safety issues, including a lack of fire sprinklers and a staircase made of wooden pallets.

Many have called the warehouse a “death trap” and said Almena’s negligence — combined with his careless drug use and partying — likely played a role in the fire.

“I don’t think it has anything to do with the people who were at the party or even some of the people who lived there,” Benavides said. “I just think he’s just selfish and negligent. He’s always, ‘Me, me, me, all I care about is myself.’ He neglected to take any action as far as the safety of the building while having people in there, that’s just total neglect. I think he deserves to go to jail.”

Almena’s father-in-law, Michael Allison, agreed — saying he wanted the self-described “thriller love child of Manson, Pol Pot and Hitler” to be punished to the fullest extent.

“[Almena] needs to be sent away to prison for a long time because he’s a menace, he’s an absolute menace — a plague, a danger,” the dad told the Daily Mail. “He’s crazy, I mean the guy’s completely crazy.”

According to Allison’s dad, the couple had their three children taken away from them last year because of their drug problems. He told the Associated Press that Almena wasn’t a good father, mainly because he was selfish.

“Honestly, I don’t think he is capable of feeling any kind of remorse or guilt,” Michael said. “I’ve never seen him ever really care about anyone else.”

Almena posted on Facebook in May 2015 that he and his wife had been “unable to see the kids for one month as we have been working and looking for the right lawyer as well as fighting extreme depression and an overwhelming longing for our children.”

But they were eventually able to regain custody in July this year following a court hearing in LA, the Mail reports.

“Someone obviously dropped the ball between LA Child Protective Services and the Oakland one,” Allison’s father said. “They were clearly not communicating, there was no follow-up, apparently.”

Michael claimed one of the biggest reasons he wanted his daughter and his three grandchildren out of Ghost Ship was the fact that Almena frequently transformed the two-story art studio into a drug-filled sex den.

“I have heard stories of sex parties from several different people … used condoms on the floor,” the dad said.

Boudreaux recalled how Allison’s sister one time witnessed a truly horrifying sight following a “huge orgy on the second floor,” involving one of Almena’s kids.

“She found the youngest [of Almena’s children], who was 3, chewing on a used condom,” Boudreaux told the Mail. “She put it in the CPS (Child Protective Services) report.”

The couple was also known to ditch their kids for days on end as they tended to their marijuana plants in NoCal, Michael said.

“They were growing pot for a while in Mendocino,” he said. “They would make a stash of cash and then they would go to Bali. They would stay in Bali for a few months and have somebody watch their kids. And then I heard from friends that they mainly just did drugs the whole time.”

Family and friends told the Daily Mail that Almena’s children were ecstatic to get out of the Ghost Ship warehouse when child services took them away.

“When the kids were removed and were with family, I had called them on several occasions to check on them,” Boudreaux said. “The little boy, who wasn’t even 4, said, ‘Thank you for helping us get out of the scary warehouse.'”

Allison’s father told the AP that Almena was in complete control of the building — as well as the vagrants who were living inside.

“He was able to cast a spell on someone in a weird way that I just do not understand,” Michael said, recalling how Almena practically brainwashed his daughter and even talked her out of leaving rehab on numerous occasions.

“[He] surrounds himself with people who are going to treat him like he’s some sort of guru,” Boudreaux told the AP. “He enjoyed having minions around to do his tasks for him and help build this great — he thinks he’s building this artistic empire.”

Almena’s father-in-law said his main concern is now for the welfare of his three grandchildren.

“I am very worried about my grandchildren,” he said. “I assume what’s going to happen is they will be taken again, I hope they will go back to Derick’s sister. She’s a completely reasonable person, and Derick’s mom is also down there and she’s a good person. Neither one of them want anything to do with Derick, they are the ones who took the kids before, so I’m hoping they will be okay.”

With Post wires