Chinese Boys In American Family Only Stay At Home And Eat Junk Food Since Two Years. Normal?

Hi.
My mom is renting two rooms to two Chinese boys. They live with us since two years now.
What I have noticed is that they don’t go to school. They stay at home all day and play online computer games on Chinese servers and watch Chinese movies. They don’t do sports or socialize with other people. They sleep during the day and are awake during the night. I assume they live by the Chinese clock. Besides they only eat junk food and drink Coca Cola. When they smoke cigarettes they only smoke it the half way. There are much more wired habits I wont list right now.…
I honestly don’t know much about the Chinese people or culture. But it occurs to me that they are wasting their life, money and health.
My question is this: Is this normal? I have read that most Chinese families only have one kid (Law thing). So can it be that most kids are mama’s boys? In those two years they never cooked Chinese food or anything healthy (Microwave pizza is their favorite.) I assume they don’t know how to cook.
They pay their rent on time, which is a good thing. Money doesn’t seem to be an issue.
Thank you for clarification.
Respectfully