I was awarded joint custody with child's grandmother now 10 years later find out he is not my biological child so I took him to his biological mother and left him there with her can I be chrged with abandonment. His grandmother refused to allow him to live with her when he was accused of molesting his 6 yr old sister.the case was dismissed for lack of evidence. He returned to my care and my wife and 6 yr old daughter moved out of our family home because my wife did not want them to live in the same house, after a yr I found out he is not my biological child

If you are the legal parent of the child (regardless of biology) you continue to be responsible for that child until you are no longer the legal parent. While you can't be charged with abandonment, since you left the child with a (hopefully) responsible adult, there are other things you could be charged with. Since custody was removed from the bio mother (I'm assuming this since you said it was awarded to the grandmother), then there is an assumption that she may not be fit or responsible. This could leave charged with endangering the welfare of a child.

I'm also not clear on what has happened here. You state the grandmother has kicked him out even though there was no evidence. Now you are saying your wife moved out with your daughter again with no evidence.

Does anyone care about this child? Is it any wonder that he may have issues with the way he's been treated (assuming he's a male).

If you have been the legal father for 10 years it may be too late to challenge that, even if DNA shows you are not the bio father. Laws on this vary by locale (which is why ANY question of law NEEDS to include your general area).

And after 10 years of raising a child, how can you not feel he is yours no matter what a test shows ?

Next how did you find out he was not yours, what made you do a test ?

Why don't you want to raise him ?