<human>: My boyfriend and I have been dating for almost exactly 4 years, and his brother, who is 18 months older, started dating his (now) fiancee literally 5 days after we started dating.

It's created a somewhat weird situation, as his brother (26 yrs old) and his bro's fiancee (23F, like me) are getting married and moving in together, and they have been dating for the exact same amount of time as us. BF comes from a traditional family, who doesn't let us stay in the same room together when we go to his house (I don't necessarily understand this, but I respect it). 

However, we (BF, BF's bro, bro's fiancee) are all going on a trip together for the 4th of July with his family. They're letting his bro/bro's fiancee stay in the same room, while me and my BF are not allowed to sleep together. I understand that they're engaged, so maybe now it's more "appropriate," but I feel kind of weird about it because my BF and I have been dating for the EXACT SAME amount of time that they have. And the fiancee is my age! 

I mentioned this to my BF, and he said I was being crazy.

Could you distill the essence of the text into 1-3 sentences?
<bot>: Am I justified in feeling weird that my BF's bro is allowed to share a room with his SO, while I can't share one with my BF?