You cannot force anyone to like you or reply to texts, FB messages etc, if he doesn't want to see you or have anything to do with you then that is his choice. Why not just get on and live your own life, visit the children that want to keep in contact with you, don't worry about what that son is doing or not doing, it will just eat away at you. I have a similar situation, I have tried many times to contact 2 children from a previous relationship, one is 28 and one is 26, they have told me in no uncertain terms that they want nothing to do with me, they don't even want to hear my side of the story, it went on for about 6 years then 4 years ago I decided to get on with my life, there is nothing I can do about it, they have great contact with many members of my family and they know where I live, if they knocked on my door I would welcome them in, I can't see that happening and I'm not going to let it get to me, its their choice. Put it to the back of your mind and enjoy the contact that you have with your other children, if in the future your son decides he'd like to see you then welcome him with open arms, no questions asked, in the mean time, get on with your life!