If my son lived with me more than 6 months can I claim him even if in an old court agreement dad gets to claim him every year?

[PhilipK]

To claim your son as a Dependent he must Meet all of these requirements:

https://ttlc.intuit.com/replies/5187060

The requirement might him unable to be claimed as a Dependent by you is

They aren't (or won't be) claimed as a dependent by someone else.

IF Dad claims him, you cannot.

I hope this helps.