My ex husband bailed on us (no PTSD there, just a prick). He has no desire to be in my kids' lives, even though he was there in the home when they were babies. He can see them and talk to them as much as he wants... Haven't heard a peep out of him in years. We tried inviting him to my son's graduation... A literal engraved invitation... No dice.
I used to knock myself out trying to foster a relationship between my kids and their family on their father's side. He also had a child, from an affair he had while we were married, that he never met, and that nobody knew about. The mother approached me, and I bent over backwards so my kids would know their half brother.
It was useless, and turned into a shit show. The half-bro is a total delinquent in and out of custody in the juvenile legal system. He only contacts my kids to ask for weed money or a place to crash when he runs away. We won't get into his mother, who I call my "baby-mama in law." Half-bro gets the asking for money thing honestly. My kids' other relatives don't have any interest in being part of their lives. Now that my kids are teenagers/young adults they have no desire to be around any of them. They just turned out to be more sources of pain for my kids. They were more blood relatives who didn't love them.
In hindsight, I shouldn't have bothered. It wasn't my job to fix that mess. It was squarely on my ex-husband's shoulders.
We had plenty of love and happiness in our own little family. They didn't need those assholes anyway.
I can understand the dilemma though. I did the same thing. Hopefully it works out better for you and your little one.