Frank has a sibling rivalry with Uncle Joe. When Manny started potty training, Uncle Joe insisted that there was a "potty monster" that was about to get him, causing Manny to fear using the bathroom, so that meant Frank had to change his diapers for a longer time. Greg says that he could hear Frank cursing to Joe when he changed more diapers from Manny because of it. Also, Uncle Joe's children call their uncle "Aunt Fwank", which Frank swears he told them to do on purpose, but Susan thinks it's cute. In Dog Days, Greg mentions that he tried to make Uncle Joe convince Frank to get a dog, but that did not work out. He also mentions that his dog, Killer ate most of Greg's birthday cake.