Some cats do suckle. Shrug. One could wish that Simba would defend himself so that you wouldn't have to. It would seem to be a self-comfort thing. Our vet suggested that our cat, Indigo, who likes to nuzzle and knead, was probably taken from her mother too early, and that if we didn't care for the behavior, we should discourage it, and she would probably outgrow it. She is now 6 years old and shows no signs of completely outgrowing it, though she doesn't do it quite as much. Please note: we didn't really mind that she was nuzzling (and leaving little wet marks on our shirt), so we didn't do much to discourage her - unless you call petting her while she was doing it discouraging (heh). Sorry that the suckling is so intense as to disturb everyone. I have rambled on and have no suggestions - so I apologize for having taken up your time - but I do hope that maybe your cat will "outgrow" the need to suckle, or that Simba will grow more assertive in fighting her off.