Any Suggestions for this situation?

My Sister and her husband split.She is moving from Northern California,to New York. He is not.Now,when he left,he left his cats behind at my sisters.She can't take them with her as she is driving and the cats are so old,she doesn't think they will survive the trip.The cats are 15, 14, and 8 yrs. She also has a very,very old, Old English Sheepdog which is almost blind and needs boo-coo attention. She is Taking Mia the dog with her. He wont come and get his cats, she doesn't want to leave them at the animal shelter (no one would adopt a 15 and 14 yr old cat) How can this be settled? Thank You for any suggestions