My husband's son found me through FB and would love some advice...

My husband and I have been married for 13 years. Abour 9 years prior to that he got his then girl friend pregnant and she had been cheating on him. So he denied the baby and after it was established the baby was his he wanted nothing to do with him. But he did provide child support for 18 years. When we met I had a 4 year old daughter and after meeting her and spending time with her he told me about his son. At that point he was 9 years old and he thought it would be best to stay away because he had a stepfather who was raising him as his own son. Through the years we talked about what would happen if this boy ever came to my husband. We had a child together and just turned 9. While my daughter knew about the son, we never knew a right moment to tell my son that his dad had a son out there and he had a half brother. When I got home from NYE I had a friend request from his son on both MySpace and Facebook. I though..whoa.. but I messaged him and asked if he wanted to talk to me because I was sure it was obvious he knew who I was. We messaged and he said he knew my husband was his father and he wanted to know if he had ever told me and if he had any brothers or sisters and what he was like. We emailed all that day and then I told him that I had to let my husband know and if that is what he wanted and he did. I told my husband and he gave it a day and told me that he would love to talk to him the next day and if he could call him. I relayed the message and my husband called him on Sunday and set up a time to speak to him the following Sunday. But in the meantime we had to tell my 9 year old who actually took it very well but had lots of questions and emotions over it. While my husband wanted a casual relationship , the son wanted more. He wanted to meet us and he has been emailing and texting me every day. Not.. my husband and now I am getting attached. He wants a relationship with Dan but also with all of us. We are meeting on Sunday for lunch. I have suggested that maybe just my husband meet with him at first but Derrick wants to meet with all of us. He feels that he can talk to me. My husband works alot and doesn't use email or texting . I feel that my husband may not want a close relationship nor does he have the time to establish this bond that I have in a week. He is my son's half brother and I want him to be a part of our lives maybe more than my husband. He is now 22 years old and married. Do I need to let my husband handle this or do I keep the contact that obviously this boy is craving. He said he doesn't get along with his step dad at all becaue he felt that he was never his son. My daughter who isn't my husband's has a really tight bond with him and we have made a family together with the 4 of us. I am afraid this boy won't accept her into his circle but she is my son's sister and we have never called it anything but sister. i am just so confused over this. I have read everyone's story and would just love to have some advice. Maybe I am thinking fairy tale when I need to think reality. Could someone please tell me how to proceed with this or am I doing the right thing?