Most Helpful Girl
That's a good question, and it entirely depends in the jurisdiction you live in. Pets are legally considered property, no different than material property like a car or household appliances, etc. I know that sounds terrible to say, but that's just how it is. Pets are not children. The couple in question has to get along well enough to decide where pets will go, if they don't want a judge to decide for them.
My husband and I have two dogs. One is older than the other, but they are both very bonded to each other. Ideally, we would take one each if we ever split up. That's actually the agreement we have in place, but on the other hand is it fair to split up a bonded pair? THAT'S the hard question that would have to be answered. I hope I never have to answer it, though. Lol.
Most Helpful Guy
The couple should make a rational decision, based upon with whom the dog has bonded the strongest and whose future living arrangements would be most suited to a dog.
When my last cohabitation situation ended, I got custody of the cat.
There was a mutual loathing between the human female and the cat.
He showed himself to be a much better judge of character than I was.
I learned to not trust anyone who did not like cats, or whom cats did not like.