Do yall ally individual nations when youre in a coalition?

I ask since it was a point it contention in a 4x game, I had allied texas even tho our coalition was full, since he was offering to protect our gulf coast in america; i accepted his mutual share map, and he was holding up to his offer, however my allies were upset that i would ally "an enemy".

I saw him as a useful one, and if nothing else someone we can come back to after more pressing threats are taken care of. Was I wrong to ally him? Or is it fair enough to think him a srategic ally temporarily?