How Much Food to Feed 4 & 5 Month Old Kittens

Thespis is 5 mos. and weighs 6 lbs. Aria is 4 mos. and weighs 3.6 lbs. I currently feed 1 lg. can grain free Blue split between them per day (1/4 can am and pm). They both free feed Blue kitten kibble (grain free) in between. A little history, they started off eating a mix of different supposedly higher end cat foods same amts. of Science Diet wet and Iams dry (since found out there is soy in Science Diet and other junk in the Iams) and switched them about 2 wks. ago. Thespis will inhale his wet food, and try to eat Arias (she eats slower, and not quite as much in one sitting). Thespis is noticeably much larger (taller and fuller around the middle), than Aria. Should I feed him more wet food? I'm not sure at their ages, how much I should give. I'm concerned that Thespis may end up fat (big belly already). Any suggestions would be most welcome. Thank you.

At that age, I would certainly think you could feed them 1 full can EACH per day.  BUT, if he is already getting a little chunky, then you need to either cut back on the free feeding, or at the very minimum, make sure he doesn't encroach on HER canned food.   I'm thinking both.   Or just feed canned so you can really monitor it completely.  Are you home during the day?   As far as how much to feed, just know that whatever the cans or bags say, it's usually on the high side. You might want to check with your Vet as to how much they should be eating, although they'll probably say "as much as they want" 

I know, I know, everyone always says let the kittens eat as much as they want.  Well I did that very thing when I had 2 "toddlers", and I ended up with one very overweight youngster.  When he was 1 year old, our Vet said he needed to lose 4 pounds!  I was shocked.  I knew he was a tad heavy, but never guessed he was THAT big.  So now 6 years later, I still have to monitor everything he eats, just to maintain his weight.  Every treat, every single ounce that goes in   And he still eats so fast that I have to stay with them while they eat to make sure he stays out of the others' dishes while they finish up.  (I feed him on the floor and the other two up higher for easier monitoring)

Thank you so much for answering. I was told to feed as much as they want, too. I put him in the bathroom and let her eat her wet food, when she was done, I let him eat. I will monitor their dry food.  I will have to figure out how much it seems they share their dry food and water, but mostly share her dry food. Maybe I should measure out a set amt. and leave just the one bowl. Thank you!