No one new to the mix?
What about the Equinox 5?
"I don't care if you're a mass murderer, take your shirt off."
Kim fraks children.
Seven had a baby.
Kim didn't try to boff him because he was a him.
That was certainly a mother and son relationship, and Seven was well into it.
Maybe like the doctor she was scared off further babies after the tragic and early death of their kid? Then having Mulcahey (the genetic sample donor) wandering about like a Ghost couldn't have helped.
Being scared of babies is one reason to avoid a relationship with the opposite sex.
I've often talked about how mangled her sexual organs probably were in the beginning (and her internal physiology in general. The Doctor kept pulling out of her chunks of metal the size of your fist that kept growing back. Everything important yet ordinairy was pushed up over and into the strangest locals.) so when she hit on Harry in Revulsion... It's quite likely that she didn't have a working vagina, or a vagina at all. Just a storm of scar tissue and half sunk technology, but anyway if at that point, so early in her development/recovery Seven was like a barbie doll down there but she was offering sex to young Kim...