Aside from the insecurity of the friend and her ownership of her DH and classing her single friend as wanting any man within reach [I've experienced this and it is really insulting]...I really do not like the sound of this friendship.
To suddenly increase the intensity of the friendship when OP was pregnant, to 'want to treat the baby as their own' [what!], call some man OP hardly knows 'Uncle' and hand the daughter over to him is overpowering and controlling, and over stepping boundaries in spades.
I particularly do not like the friendship being classed as 'family'. They are not family. They use the phrase to wriggle into the OP and her daughters life even more. It's weird. What is their agenda? They should back right off so this incident is an eye opener to the OP and she should be glad to see how weird this all is...and get right away from them.
In my life someone has insisted over and over that I was 'family'. I found it very annoying. She was not 'family', I have my own and she is not part of it. I hated it when she said it. I took a step back, watched and waited and now I've walked away as I could see her agenda playing out. Me being in her life was very useful to her, like an insurance policy.
It was used as a way of keeping me in her life no matter what, no matter how rude, snappy, bad tempered and manipulative she was...a way of control for her benefit. Certainly not for my benefit as she didn't like anyone in my family but I had to adore those people in hers. In her words 'people in families snap at each other, get angry and fall out all the time'. [Not in my experience/family they don't as my family is quiet, hers are always having disagreements ].
In her head that meant she could talk to me in any way she wanted when she wouldn't talk to any other friend like it! It was very odd, quite disturbing to think she thought I could be taken in and played.
In the OP's case I find the interest in the daughter creepy to be honest, especially that from the man. OP should leave them both to it, walk away with her daughter and find better, genuine friends.