How old is Frankie now? I really don't see this as a problem. This is just an issue that will come up when kittens are taken away too early. Growing up, my family had a calico cat that sucked on her paw. She did this her entire life, and she was otherwise just fine. As long as Frankie is happy, that's all that matters! What a cutie-head!! Be sure to kiss him for me!