I have two kittens, not from the same litter. The older kitten is 5 months old, and I have had her for 3 months. The younger kitten (not even half the size) is 3 months old and I have had her for 2 months. The older kitten was already quite a bit bigger than the younger kitten when the younger kitten joined us. No, it is not the older kitten stealing the food!
Younger kitten suddenly morphs into what I call "piglet-face" as soon as she realizes it's time for wet food. She gulps it back as though she hasn't eaten in days, and then beelines for older kitten's food the instant she's finished hers. There are two bowls of dry food out at all times, so she is not starving because she is eating that regularly throughout the day. Older kitten has never tried to get at her food while she's eating, in fact, older kitten eats very slowly and calmly, likes to eat some and come back for the rest later, and when younger kitten comes and shoves her face into older kitten's bowl, she makes no attempt to stop her, just sits there looking put-out. Older kitten does not act passively like this in other situations though (playing, lap-sharing, etc), she has no problem standing up for herself, or just being plain saucy, then.
Younger kitten does not have worms, so it isn't that (older kitten was actually very dirty with loads of fleas and really bad worms when I got her, but got rid of them before younger kitten joined us).
I have tried putting older kitten's bowl in a higher spot away from the usual food area, but this seems to put her off her food a bit (maybe it seems like punishment?) and younger kitten gets it anyway. I have tried putting younger kitten in the bathroom with her food until older kitten has finished hers, but like I said, older kitten likes to eat her wet food in 2-4 different goes, so not fair to younger kitten if she is locked in the bathroom that whole time (plus the litter box is in there, so it means older kitten would also be locked away from litter box...just doesn't work).
Is there any way I can teach younger kitten to slow down and/or stop stealing older kitten's food? Or teach older kitten not to let her food be stolen? Or just some suggestions for eating arrangements so everyone gets to eat their own food?