INFO: Was Jay included on these discussions of living arrangements at all? He's not the home owner, but regardless of whether or not he pays bills, I would assume him being your brother's (I assume) long-term partner would warrant him having something of a say of what he is or isn't comfortable with.

To me right now, it sounds like Jay is reacting to a situation he didn't know the full details of, or even any details at all. He's a person you're moving in with, too, not just your brother and kids.

I'm inclined to say E S H because of this; you and your brother for excluding Jay, but also Jay for trying to tell you to get rid of your dog. No one here seems like they handled this arrangement maturely.

Also, keep an eye on your dog in case Jay tries anything.