How should i feel about this? Issue with boyfriend's relatives?

If you're expecting this to be a long, LONG relationship, you're gonna have to find a way to have a good relationship with his family. Blood's thicker than water, and if you raise tensions there it's only going to create problems and stress for your boyfriend. Perhaps they do let friends stay over for long periods of time, but are they friends who may be having "relations" with their relatives while in their home? Allow your boyfriend to have time with just his family, time with just you, and spend a bit of time with both him and his family all together. If you want this to be the serious relationship you say it is, you have to make all of those dynamics work.