My teenage son does not know his real father

What age should I tell my 15year old son that his father is not his biological father?  I fear that to tell him when he is a teen could be upsetting however I also feel I am cheating him out of knowing his bio father while he is young.  He actually knows him as a friend of the family but has always been raised with my ex husband as his dad. His biological dad has been asking for him to be told.

[margypops]

I think it is over due , Yes tell him, he should know he will want to get to know his bio Dad ,he will have 2 Dads that sounds pretty good, just explain to him.... kids are very accepting of circumstances. Good luck to you all .