AITA for wanting to wait a few weeks on taking this dog

So here’s the story.

I’m 54, my wife 51. We’ve been together for 6 years, married for 3. Her twin sister very tragically just passed away before Halloween.

The sister had two dogs. One went with the adult son. Other one went to the ex (who is still raising their teen).

Apparently, the dog was not fitting in well there so the ex asks my wife if she wants to take the dog. This is a little over a week ago. We already have 3 dogs and I really, really didn’t want to take on another dog. BUT given the circumstances I eventually said OK but please give me until end of December. I just wanted a bit of a break due to all the emotional madness we’ve been going through since her sister died 5 weeks ago. I thought this was reasonable. She agreed. All good.

My wife’s 22 year old son though (living with us, not working) decided to go to South Carolina (9 hours away) for Thanksgiving week and even though he knew this was the decision, and even though I texted with him about this directly and said hey here’s what we decided to do (get the dog after Christmas)… he still brought the dog back with him. Today.

The son thinks I’m unreasonable. The wife now just won’t do anything other than say “well I told him not to bring the dog…”.

I feel like I have no agency at all now in my own house. Help me out here.