My 14 lb Cavalier King Charles Spaniel became friends with a 140 lb Preso. Always supervise them so there is no accidental injury. But after awhile they learned that running and chasing was the way to play. Not jumping on each other. Although the big guy would grab my guys long ears occasionally. My guy can run under him. He tried to do it to my guy once and acted astounded when my guy tumbled over. After a good run, my 14 lb guy uses the 140 lb guy as a pillow! But always supervise them cuz big guy doesn't know how big he is!