I don't think this is a problem . Be sure of course that you give them a good quality of food then , well balanced , containing enough vitamins , etc. ! Hill's cat-food is perfect ; they only difficulty you can have with "adult"-food , is that the pieces are to big for kittens' teeth ... ; but 6 months , that should be okay !
My little Inka also often eats from Maya's bowl ...
Whenever I wanna give Maya something that is not yet suited for little Inka , I take maya into the kitchen , ON a cupboard where she's allowed to jump on . Of course the lil critter is meowing my ears off then ... LOL !