"I don't know if you saw [Sara Foster] jumping on top of Kate like a psychopath but we were just so excited about her having a girl," says Erin Foster

By Jen Juneau and Mariah Haas
April 09, 2018 05:31 PM

Erin Foster‘s stepbrother Danny Fujikawa has quite the love story with her best friend, Kate Hudson.

“Her baby daddy, Danny, is my stepbrother,” the comedy writer told reporters Sunday of the 38-year-old third-time mom-to-be (who’s pregnant with a baby girl) at Daily Front Row’s fourth annual Fashion Los Angeles Awards.

“It’s a really beautiful connection because … our parents got together when [Danny] was like 15 years old, so Kate has been [a] part of our family,” added Foster, 35, explaining of how the tides shifted, “She [was] having dinner with us, and they’re there, and then all of a sudden they looked at each other differently after 15 years, and suddenly they fell in love, and it was this crazy thing to witness.”

“She kept going, ‘Well, wait a second. Me and Danny can’t be a thing. It’s not a thing, right?’ ” she recalled. “And we’re like, ‘It looks like it’s a thing!’ And now they’re having a baby. It’s just really amazing.”

Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.

Melissa McCarthy And Eric Buterbaugh Host Brian Atwood's Celebration of PUMPED
Credit: Donato Sardella/Getty
The Daily Front Row Hosts 4th Annual Fashion Los Angeles Awards - Inside
Credit: Stefanie Keenan/Getty

“When I say timing is everything, it’s so true, because you’re around someone for so long and you’re both not ready to be in that long-term relationship, and you’re young, and you go through other relationships and you don’t think of each other that way,” Foster told PEOPLE.

“And then one day you look at each other differently and you don’t have to put on any airs or pretend to be somebody else or try to be cool because you already know each other,” she added. “They just found each other at a really beautiful time in their life and it just happened so seamlessly. She kept going, ‘Is this weird for you? Is this weird for you? I won’t do it if it’s weird for you.’ And we kept being like, ‘It’s not weird. It weirdly feels right.’ ”

“We” would be the star and her sister, actress Sara Foster, whom Hudson is also close friends with — and had a sweet cameo in the latter’s gender reveal video.

“[Kate] wanted a girl so badly and they really didn’t know until they popped the balloons and pink came out, so it was really exciting,” Foster told reporters. “I don’t know if you saw Sara jumping on top of Kate like a psychopath but we were just so excited about her having a girl.”

RELATED VIDEO: Kate Hudson Celebrates ‘First Date Anniversary’ with Danny Fujikawa: ‘So Much Pure Love’

Hudson is already mom to sons Bingham Hawn, 6½, and Ryder Russell, 14. And while Foster hasn’t given any advice to the couple since she doesn’t have any kids of her own, she doesn’t think they need it anyway.

“Kate is a really good mom. She’s strict. She’s really good with boundaries. She’s tough,” Foster told PEOPLE. “And Danny is like a hippie. He’s very ethereal and go-with-the-flow, so it will be interesting to see how that happens.”