It depends on more details. You may need to have your taxes done by a CPA.
Was this an investment house or your son's home? Did you have money invested in it or were you only on the deed to help your son acquire the home or mortgage.
If it was an investment house, the taxes can "follow the money". That is if your son got it all, he can report all the gain.
However if he is claiming the home sale exclusion, he cannot not use that on your half of the gain. You have made a gift of equity to him and are responsible for your portion of the gain on the sale.
