Zarin, the “Real Housewives of New York City” star, used a sperm donor to conceive 27-year-old Ally, after struggling to get pregnant with then-husband Steven Shapiro.

In 2013, Zarin posted on an online service that helps the children of sperm donors find their siblings — and quickly found a woman who said she was the daughter of the same sperm donor.

Ally met the woman and she quickly developed a long-distance friendship with her — and three more half-siblings.

“I’m an only child, so it was nice and exciting to have an extended family,” Ally told Page Six. “It was like, ‘Welcome to our club!’ ”

Ally says they “checked in on each other” and sent each other messages on holidays. But, she said that she had a gut feeling that prevented her from getting too close to the group.

Then in January 2019, one of the half-brothers found their father through DNA analysis service 23andMe, forcing Ally to wrestle with whether or not to start a relationship with her biological father.

In April of that year, Ally got her own match with a man who claimed to be her father and, in fact, shared half her DNA — making her realize that she’d spent years with “siblings” who weren’t related to her.

Ally tells us that her gut instinct that kept her from forming too close a bond with the group saved her from heartache.

“I think if I had a deeper connection, I would have been gutted,” she said. But “I felt like I’d been lying to them all these years.”

She hasn’t decided if she’ll meet her dad, with whom she’s exchanged e-mails. “Because of what happened, I’m a little more hesitant,” she said.