The phrase "cat brother" typically refers to a person who has a strong affinity or connection with cats. It may imply that the person understands, loves, or relates to cats very well. Full definition
The villains of the piece, fat - cat brothers who intend to plunder the district by putting a dummy in office to do their bidding, are obvious, uninventive characters that John Lithgow and Dan Aykroyd could play in their sleep, and nearly do. (indiewire.com)
I love sharing my life with my little pug and her big fat cat brother. (sugarmommaclub.com)
View videos of the life and times of a puppy mill rescue dog, including day trips to the beach, weekly rehab, and funny clips of her dog brothers Wylie and Spencer and cat brothers Jack and Miles. (CAPS-web.org)