That's may be a bit young for them to only be on two meals a day unless they had themselves stopped eating most of one of their previous three meals a day. I've had young dogs switch to two meals at around 4 months but most would be closer to 6 months and many breeders feel it is better to keep them on three til about 6 months. But pups often just decide for themselves before then that they don;t want the third meal :lol:. If still eating it, I'd leave them on three til they start ignoring the midday meal (which they will gradually tend to do).
Puppies all vary so there is no real rule. Most puppies will eat about a cup of food a day, some eat less. Maybe this food has a lot of filler/fibre but 1.5-2 cups sounds an enormous amount for a cavalier puppy! Has he been checked for worms recently? Most foods tend to seriously overdo it when giving estimated amounts -- that's certainly what vets and breeders tend to say and has also been my own experience. Dogs all have different metabolisms and vary but wow -- I have very active dogs and none eats more than a cup a day of anything; Jaspar is the most active and largest at 17lbs and gets about 3/4th a cup daily, just for comparison.
Just a caution
-- if these two puppies are different sexes you will need to start keeping them apart soon as they will begin to be able to be sexually active and that can start as young as 4-5 months. Your vet can advise -- even if neutered males can still impregnate for many weeks afterwards so it is important to get good guidance.