My kitten is a hungry hungry hippo on Backcountry

So, as the title suggests, my 5 month old kitten is always hungry so I'm not sure if the food I'm giving him is good enough for his dietary needs or if I'm simply not giving him enough food daily.

He was on the Science Diet Kitten Formula when I adopted him, but I switched him over to Backcountry Raw Infused cat food, because that is the food I feed my adult cat. I read a lot of terrible reviews about the Science Diet food.

I put my adult cat on Backcountry Raw Infused food because she's spoiled and it's the most expensive food in the store, and the pet store owners claimed it's the absolute best you can find. But they also said because it's so packed with protien that cats wouldn't need to eat as much of it so it goes further, and that does not seem to be the case at all! My adult cat still eats lots. I know Backcountry makes a Kitten formula, but I read the ingredients on it and looks exactly the same as the adult formula so I just went with the adult food because my adult cat eats it anyway, but I wonder if I should actually get him a kitten formula. 

The kitten seems to be healthy and is growing, very playful. He sometimes gets constipated (tries to use the litterbox but nothing comes out) but is peeing alright, and I can't remember if that started while he was on the Science Diet or after I put him on Backcountry. Either way, the constipation never lasts for long and he isn't showing any other bad symptoms.

My adult cat is fat and she overeats if I leave the food out. She's on a diet right now (I'm only feeding her twice a day now, whereas before I just let her graze all day), but I swear since being on this food she is shedding more and has developed dandruff. She has had an issue with vomitting/hairballs for a few years now, that started before I put her on the Backcountry. Just recently I noticed her vomiting directly after eating, I think because she's eating too fast or overeating still, despite my attempt at portion controls. It may be that the portions I'm giving her are still too big for her, but I'm still kind of worried about this food despite how awesome everyone says it is.

I'm feeding them both the Backcountry kibbles and also the wet food packets. But because it's so expensive, I split the wet food packet between both of my cats every morning, giving my adult cat a bit less than the kitten. Then I also give them 1/3 cup of dry kibble with that. Then at lunch I give the kitten half a cup of dry kibble, another half cup of kibble at night for both of them, and sometimes another half cup for the kitten if he's still hungry at night, but he's still acting like he's hungry all the time.

When I brought him to the vet initially, she said he was getting a little chubby in his belly so by the time he's 9 months I would have to put him on a diet and she recommended not free feeding, which works because I'm trying to stop free feeding my fat adult cat. 

They both loves backcountry, but they both seem to be foodies, they both love any food I give them, maybe a little too much. But he's taking it to the extremes. He even gets into the garbage and is a little beggar while I'm cooking or eating, you'd think I never feed him at all considering how he is constantly scavenging for food.

I should also mention that my adult cat preferred his science diet food over the Backcountry. He seemed to like the backcountry better, but they also like to switch food bowls often, so it might just be that they prefer to eat eachothers food over their own.

Also, I would be open to other food recommendations because it is starting to get really expensive to buy that stuff, considering how much the hungry, hungry hippo eats in comparison to my adult cat.

It would have been nice to have gotten a response.

I ended up deciding not to go with the Backcountry again, told the girl in the pet store of the issues I was having with it and she said one other woman had reported that every time she got to the bottom of the bag, her cat would start throwing up. When she switched to another brand the vomiting stopped. But my cat was vomitting before Backcountry, so...

I decided to change it anyway, I went with Taste of the Wild trout cat food for her. It's a lot less expensive and seems to have great ingredients but it has a lot of amazing reviews and also my instincts told me it was good. I grabbed an actual kitten food for the kitten, but he's still wanting to eat way more than the recommended feeding amount on the bag. It says he should get about a cup of food a day, but he eats more like 3-4 cups of food a day and still seems really hungry all the time, and he's not fat and he was dewormed.

I still don't know what's causing my adult cat to throw up. I thought maybe it was an allergy to chicken, but yesterday morning I gave her Backcountry wet food with rabbit that has no chicken ingredients in it, and she licked off the sauce only and regurgitated up a yellow frothy bile next to her bowl, then wasn't interested in eating after that.

She used to like the wet food, and also she used to like when I soaked her dry kibbles with some water but now she seems to prefer the dry kibble. She likes the new Taste of the Wild food, but prefers to eat it dry. That's fine because she's a good drinker. 

There could be more than one thing causing her vomiting. I did some more research and because she's otherwise healthy, it sounds like it could be too much bile forming on an empty stomach that causes her to regurgitate and maybe eating too quickly. So I'm going to try to give her a tiny bit of food right before she eats to help it soak up the bile, and then separate the cats in different rooms when they eat so she doesn't feel like she has to eat it up fast (because he does eat his and then come over to eat her leftovers, so that might be making her eat faster).

But... I don't know, because she was vomiting before I got the kitten, but never close to her food bowl, I would end up finding it random places in the house or seeing her vomit random places in the house, usually a mixture of kibble and hair and a blade of grass. But I don't know if they were typical hairballs. This was when I was free feeding her, so I never knew if she had just eaten, but probably she had, because she used to eat tiny bits very frequently throughout the day.

We had a cat who was a vomiter. Didn't matter what we fed him. We ended up just giving him many small meals throughout the day. That helped but didn't solve the problem.

The two bros we have now would eat us if they had the chance so we can't just leave food out for grazing. One is overweight and one is a more decent size so we have to make sure the bigger one doesn't hog

Haha, well it's my kitten that's doing all the hogging despite the fact that she's the fatty, but I'm making sure to keep them separate during meals now.

She didn't throw up yet today, so far so good, and she's really liking the new Taste of the Wild food.