Stingy cat stealing food from other cat

Hello everyone,

I have a 14 wk old female DSH (Leila) and a male DSH (around 16 weeks, he was found when he was probably around 3-4 weeks old but who knows really...this is vet's estimation). His name is Tommy. We feed them Wellness Kitten Health. He poops probably every 2 hours, LOL. It is always soft, never diarrhea. He also constantly has gas. He is getting overweight and Leila is still pretty small. He is very stingy with his food (probably has something to do with him being on his own) and will try and eat Leila's food as well. Should I feed them in seperate rooms and how many times a day for him when he needs to lose weight and for her when she needs to gain?

At 4 months many of us say FREE feed .. ie let him just eat , it could be he is approarching another growth spurt.. have they been wormed?? If yes then maybe the wellness has too many grains for him

4 times a day is normal for most at this age

We have been free feeding them and putting it in there 2-3 times a day depending on how much they eat. He had worms when we first brought him and has been wormed twice. He had a big, tight belly that was obviously worms. Now he's chunky all over. Should we switch foods and if so, to what?