Yes, Gary is the father. He’s ended up leaving her (in the future) because he found out she had the future knowledge of their daughter’s early death but went ahead with having her anyway.
!spoiler Ah? I didn’t catch that, I thought they divorced when the daughter was still alive given the parts about dating someone else? Where in the story did you catch that bit?
spoiler
Yes, Gary is the father. He’s ended up leaving her (in the future) because he found out she had the future knowledge of their daughter’s early death but went ahead with having her anyway.