I miss my dad...

I've been thinking a lot about him lately, as I do often, and once again I'm wondering how I should try to resolve things. He hasn's spoken to me in years and I don't even know why. He has excommunicated me from his side of the family and if it weren't for facebook and my amazing grandma, I wouldn't know what was going on with anyone! I'm torn because I want my Daddy (yes I still call him that and always will) in my life, but I know that even if we talk and figure things out, that nothing will ever be the same. Maybe that's all part of growing up, but I hate it. I want to be able to talk to my little brother and sister. I miss them so much. I know my step-mom has a lot to do with things, but I just feel like I need answers. I need to know why he won't talk to me. Why he is so ashamed of me or whatever. Why he doesn't want me at the family get togethers. I had my daughter at 18, and had my son out of wedlock too... but so what!? I also graduated highschool with honors, went to college, and have been raising my kids on my own. I don't live off the government, I always have a job, two when neccessary, and in my opinion, have led a life he should be proud of, not ashamed of! I've thought of writting him letters, calling him, or just showing up at his job (since he owns the place) and just get everything out right then and there. I'm angry and so hurt and I miss my dad. Life is too short and I'm terrified that this "estrangement" will go on for so long and then it will be too late. I need to know why my dad gave up on me and what I did that was so horrible that my kids can't know their own grandfather. I just want to make everything better again.