Erin Foster is thinking about adding to the Foster family tree. 

On her July 31 Instagram Story, the actress—whose parents are David Foster and Rebecca Dyer—hinted about what she would be like as a mom, but quickly clarified that she's not yet expecting with husband Simon Tikhman.

"Can you imagine how insane I'm going to be as a MOTHER!?" Erin captioned a plane selfie with a crown emoji over her head. After the post sparked pregnancy speculation, she set the record straight in another pic: "Guys I'm not pregnant. I said WHEN!! Delete all your nice DM's to me." 

Erin, 40, comes from a large extended family as her dad has been married five times. 

The musician, 73, shares daughter Amy, 50, with ex B.J. Cook and welcomed Erin—as well as Sara, 42, and Jordan, 36—with his second wife Rebecca.

In 1991, David became stepfather to Linda Thompson's kids with Caitlyn Jenner (Brody and Brandon Jenner) and then, in 2011, became stepfather to his fourth wife Yolanda Hadid's kids Gigi, Bella and Anwar Hadid.

The pair split in 2017 and David tied the knot with Katharine McPhee, 39, in London two years later. (They went on to welcome son Rennie in 2021.)

Katharine and Erin have cracked several jokes about their stepmother-stepdaughter relationship, despite their one-year age gap, and have bonded over family events.

In fact, when Erin tied the knot with Simon in Nashville on New Year's Eve 2019, Katharine honored the couple by performing a love song: Sara Bareilles' "She Used to Be Mine."

Erin has since defended her dad's relationship with Katharine to social media trolls, writing in 2021, "If I can accept my stepmom looking like this, you certainly should be able to," adding, "let her live." 

However, Erin has also been candid about coming from a different kind of family than her now-husband. 

"I am now engaged to someone whose parents have been married for 40 years," she said on the Sibling Revelry podcast in 2019. "He comes from a Russian, Jewish culture that's a thick community of family-oriented people... Very early on in our relationship, I realized this disconnect in our upbringing, because he was like, 'Erin, the number one rule in life is you always honor your parents.'"

That line surprised her. "And I was like, 'Honor your parents?!'... I had to, like, completely rebel against my parents to survive," she explained. "I had to basically tell them what I'm going to do, or else I would have been stuck in Malibu." 

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