Offered which you both identify as introverts, i do believe a fairly simple guideline is “what continues on during my room is my company” — nobody gets to bitch that one other is going out in their room way too much / having buddies within their space / making their space a pigsty (demonstrably if you will find rats operating from the space having gorged by themselves on month-old pizza, that is not ok).
Are either of you going to be squicked away by the notion of your sibling getting it in with some body behind that bed room home? Is certainly one of you a owl, while the other likes to do dishes at 7am night? You dudes understand one another and so I think you are able to probably have a better, light-but-meaningful discussion about all those sordid nuts-and-bolts compared to the average roommate gets. […]