in need of advice

hi im totally new to this and really not sure on how it works..... i really just wanted some advice if ant body has got n e 4 me....i had a son 12 yrs ago and the bio-dad has never seen him or had contact with him (that was his wishes not mine) i have since met another man when my son was almost 2 and he has always called him dad 4 as long as i can remember when my son reached the age of 8/9 we sat down and told him the truth about his real dad he handled it quite well concidering....i've always thought that it was best for him to no the truth then to find out when he was older...any way i have been with my partner 4 10yrs now and we have had 4 children 2gether we are not married and never will be all the children including my first son have my name because we didnt want my eldest child to feel left out by the other children taking my currant partners name...recently my sons bio-dad has been in contact and now wants to see his son 12yrs later....i have sat down and told my son this and his answer was he dosnt want anythin to do with him, i dont no if he is just saying this to spare me or my partners feelings i have also told my son that if he does want to see him then its fine by us but he still says he dosent he says that my partner is his dad has been 4 10yrs and always will be....but im worried that his bio-dad can take me to court to get rights to see him as he is only 12 will they take his feelings into concideration ??? me and my partner have been talking about him adopting my son but do we need his bio-dads permission ?? his name is not on my sons birth certificate.....can anyone advice me ?? meny thanx sara x