My dad cousin is my friends dads brother r we related?? If so how far down r we related and if its like 3rd/4th cousin is it legal to have a relasionship ***?

Let's see - "my dad's cousin is my friend's dad's brother." Which means your friend's dad is also a cousin of your father (assuming that by the word "brother" you didn't mean "half-brother.") Which means your dad and your friend's dad have a common set of grand parents, and your friend and you have a common set of great grandparents. You are second cousins. As for have a relationship - I am not aware of any prohibitions in the US regarding 2nd cousins.

Your Dad's cousin is your first cousin once removed, I believe. It would be improper to have a relationship with him. He and your father share grandparents so it's a close genetic connection. It would also be considered weird socially and is not really worth it.

Also, your friend's dad's brother is an entirely different generation from yours - another reason it' inappropriate.

I think the OP is aking whether its appropriate for the OP to have relationship with his friend, not with his friend's dad's brother. Hence it's a question about relationshops between 2nd cousins.