I always thought it was sad when one adult demands another adult to give up a pet. I could see it if the pet owner did not spend time with the pet, or allowed the pet to be destructive. Also if the pet owner neglected to clean up after and take care of the pet. I could also see if there was a sudden onset of allergies. When I was dating my husband....30 years ago...I mentioned that I loved animals, children, my parents among other things. I think it is best to talk things out with whoever you are planning to date before you move in with them. If they change their mind later, and the pet owner is being responsible..oh well, but I would not be the one to move. The person changing their mind would have to do that.