Cat wants kitten food, kitten wants cat food...help!

Jack is a little over 4 months old now. Asher is 4 1/2 years old. Jack of course is on kitten food and Asher is on adult food. I feed them both at the same time in the mornings but they each want each other's food. I usually put Jack in a room with his food so he can eat it without Asher stealing it from him. Sometimes Jack eats it, sometimes he doesn't. If he doesn't then Asher will if I don't get rid of it. Then Jack runs over to Asher's bowl and starts eating whatever Asher didn't eat. How can I control this problem? I try putting Jack up in a room to eat, but sometimes he doesn't eat it and I end up throwing it away. That's one less meal he gets if he doesn't eat. If I leave it out Asher eats it. I don't know what to do to solve this! Any suggestions?

Thanks!

what are they each eating??

Well if the adult doesn't have a weight problem and the cats keep switching foods, then I'd mix a little of both in the bowls

I just want to add that I am in the exact situation you are! I still have my cats seperated but when the kitten escapes, she goes straight for Mattie's bowl and when Mattie sneaks into the kitten's bedroom, she goes straight for the kitten food. Right now they are still seperated so I haven't figured out how I am going to handle it once they aren't seperated anymore (especially because Mattie is on the large size already).

I know they make all-life-stages food but I'm not sure how good of an option that truly is. Maybe someone can help me on that one?

All life stage usually is just an adult that they passed the AFFCO % s,.... Normally IMHO they are nt very good for kittens or seniors as science has shown different ages need different items or levels of the same item is different

I have this problem too! Not so much with the cat eating kitten food (he's fussy) but the kitten constantly goes for the cat food. My vet said I can feed them both kitten food since my adult is skinny anyway. Problem being, the cat WONT eat the kitten food, so I have to feed him adult food, and the greedy kitten eats both. However the vet also said so long as she's getting half kitten food, and is growing as Id expect, I shouldnt worry too much about it. Maybe give them both adult wet and kitten dry, or visa versa? Or I feed my kitten first so she's full when the adult food gets served and doesnt steal as much of it. Good luck!