Maybe a silly solution but could you agree with them that if their bedroom door is open it automatically means that you are welcome to join them if you feel like it, and if the door is closed it means they would like some private time?
That way you don't have to wonder, they don't have to bother you when they think you want some alone time, and everything will be better in general...
Another thing I've learned in my relationships is that if I want or need a hug, I inniciate a hug. Because if I don't, how will my partner know I'd like a hug?
Hugging goes two ways. If I never hug someone, eventually they'll stop hugging me as well. When I hug someone more often, they hug me more often.