Kitten & Adult Cat Feeding Question

I have a kitten that is about 4 months old and an adult cat that's about 8 years old.  Both are indoor cats.  I've read around the internet and here to feed the kitten as much as I can while it's growing.

My question is what type of food to use.

Should I use kitten food and just let the older cat eat it until the kitten turns 1 year old?  Or could I mix kitten food and adult food together?

Also, there are so many brands out there.  Which would be the better brand for them?

I can't remember the name of the brand I started out with but am currently using the Blue Buffalo Wilderness.

I had read that grain-free was better for them.  And since then have been trying to find the better grain-free food.

Any help will be greatly appreciated.

Thank you.

Most "adult" foods are labeled as for all life stages so they can be fed to a kitten. You would just have to feed the kitten more food. I never fed my Aby kitten food. He was weaned right onto commercial "adult" raw food by the breeder and I continued feeding it. He grew up just fine

Some people do like to feed kitte specific food to a kitten until about a year old. Others feed both kitten and adult foods (likey in separate bowls). This is totally your preference

There are tons of brands of food out there. Just feed whatever your cats like to eat and you can afford Grain-free is ideal. I personally like Nature's Variety Instinct and Weruva.