Sorry for the length. My mom is what is politely referred to as a "serial monogamist." She first married halfway through college and dropped out to follow her husband's job transfer (in the early 70s). Apparently they didn't have the big talks before they wed. She's always said they divorced because he wanted her to be "barefoot and pregnant" and move back to his tiny hometown, which wasn't what she wanted. A few years later she married a man 20 years her senior, and from all accounts they were very much in love. Sadly, after a couple of years of marriage he died of a heart attack, and she was a widow at 27.
After several years single, she moved across the country for her own job transfer, where she met my biological father. I guess shortly after they got married he became abusive, and she was pregnant with me, so she left to move back to her hometown. When I was very little--probably under 2--she met her 4th husband Adrian. She had gained 80 lbs while pregnant with me, she was 36 when I was born, and her self-worth was pretty low (my aunt has talked to me about this). So, though he was more into her than she was him, they married. He had grown kids at this point, but he legally adopted me, and for several years he was my dad. I called him daddy; I was a total daddy's girl. Shortly after I turned 6, she met a guy she liked at work and we left Adrian. I think he wanted visitation but she apparently didn't want to deal with seeing him or something; she told him "I won't ask you for money if you stay out of our lives."
About 18 months after leaving my (adopted) dad, she met a guy through a dating service with whom she got serious enough to move in with. Kids were not his thing, but they married a few years later, and she was with him until I was 21 (I moved out at 18). She's had a couple of relationships since then, and remarried for the 6th time 3 months before my wedding in 2012, to a guy who she'd known 6 months.
The only stable man I had in my life was my grandpa, who died when I was 18. After I could no longer be a daddy's girl, I was a grandpa's girl. I never met my bio dad and though I wanted to, he died of heart failure when I was a teenager (which I didn't find out until years later). Legally, Adrian is still my dad, but the only contact I've had with him in 2 decades was a letter I sent him 5+ years ago, in which I said I wanted to get back in touch. His response was brief and rather typical of a guy: not good at writing letters. He did say my mom would be upset if she knew I'd contacted him, so it seems like he was hesitant to continue contact. I sent him a Christmas card that same year but never heard back.
H and I are talking about TTC in about a year; I'd like my kids to have a consistent grandfather in their life (FIL lives in another town). But I also want to have a relationship with the man whose lap I still remember falling asleep in, who was the center of my little-girl world. And I want to do it before it's too late. He's in his 60s by now, and if I don't make an effort now, I have a feeling I will read his obituary in the paper one day and be filled with regret. But how? Should I just send him another Christmas card, or another letter? What do I even say?


Re: Reconnecting with my adopted dad, 20 years later
As far as your situation, I would say as much as you want a relationship with the man that you feel connected to as a father, I would reach out to him, but go very slowly and not have too many expectations on the outcome. The reason I say this is because you seem to have these high expectations of having this relationship with him and your future child, but what if the feeling is no longer mutual given the whole situation? It's not your fault, obviously, what happened between this man and your mother, but I think it would hurt you in the long run if he doesn't want to be in contact. So reach out to him, but take it slow with reestablishing a relationship.
My mom had a boyfriend when I was small (after divorcing my biological dad). They were going to get married. But the relationship failed. She still sees his parents at times. They told her that their son will not allow them to even mention my name. They said that, for them, when he and my mom broke up, it felt to their family as though I had died. I just disappeared from their lives. It was too much for him. His parents still contact my mom and ask about how I'm doing and to see pictures of me and my son. But he can't handle it. He married and had two kids of his own but that break up and losing the kid he was raising is still too much for him. I respect that and stay out of their lives.
One of life's hardest but greatest lessons is to embrace and focus on the people that will be there for you and your children. I lost someone that I thought would always be there for me and my kids, and now she is no where in sight without a care in the world for me or my kids. It hurt a lot, but I have learned to move on and concentrate on those that truly WANT to be there for me and the kids. I would focus on your FIL, other family and friends and perhaps seek counseling if you still are mourning the father figure in your life.