Three 19 year old dudes living by themselves. Like. Y'know? They're not going to be saints. It's gross, sure, but it doesn't sound sexual. Is it socially acceptable? Nah. Is it disgusting? Definitely. Is it immature? Ayup. What did you expect from 19 year old guys living together without parental supervision? 

You're dating someone who is going to become a different person in the next 5 years of their life. There is *no comparison* from 19-25 years old. They're worlds apart. That's the time people do their biggest mental growth spurt. You need to find yourself a boyfriend who isn't gross and wildly immature.