I hope you decide to keep the baby. You already know that the man is a loser. You already know that deep inside he is not right for you. You just need to have to courage to cut him off once and for all. These types of situations very seldom work out in favor of "the other woman" in the end. That is what you have allowed yourself to be. "the other woman." I have to wonder what the heck you were thinking messing with a married man. You really should think more highly of yourself. You deserve better than that!
No, you didn't know he was at first. I realize that. But, he has lied from yo from the very beginning, leading you to believe that he wasn't married with a family. Who knows what other things he has lied to you about? I wonder how many "other women" there are, too? I am sure you are not the only one! He knows no other way. He will be a lier and cheater for his entire life. Is this the type of life you want for yourself?????
I also have to wonder what in the heck is wrong with his wife that she has allowed this to go on, has allowed herself to be treated in this way? I have never known a woman not to question a man's odd behavior. It is obvious that she must think rather lowly of herself, and she does not have the courage to leave this man, even though she knows she should. She must be a very miserable woman.
As for your relationship with him after the child is born, well that can be touchy. If you completely want him out of your life you can ask that he sign over any and all rights to the child. This means he will not be able to have contact with the child, or you, and he will not have to pay any kind of support.
The other alternative would be to list him as the father, in which case he will have to pay child support. But then you run into also having to allow him visitation rights. This, in turn, will mean that he will be a constant in your life as long as his interest holds in you. Who knows how long that will be. One day he may just decide that he doesn't want the responibility of you holding a baby over his head and just up and leave you both, going back to being that "good husband and daddy" to his family.
I will warn you of this, though, I already see that should you choose this route he will definately use your child as a "bargaining tool" against you. He will use your child to make you feel guilty about any decisions you make, just as he already does this with his two sons and wife.
As for you family I say to heck with them. They are losing sight of what is most important here, and that is you and your feelings. Though they may claim to be christians, they are anything but! And god-fearing true christian would never suggest an abortion. Any god-fearing true christian should know and give unconditional love. If they should choose to cut you from their lives because of this they should be ashamed of themselves! Let me tell you that later on down the road they will very much regret doing this if they go through with it. When that time cmes it will be up to you whether or not to forgive them.