White people problem ahead, proceed with caution. 

Sorry for any mistakes, I hope it's understandable, because english is not my main language.

I'm 19 and he's 27yo. We're both at the same public university (and course). I'm entering my second year and he's on his last. Our course lasts 4 years and he's on his 7th (I don't blame him, I think he had his reasons). We live together in an apartment 4 hours away from our parents and sister (22), our parents pay all our bills. 

My parents live in the city, they bought a old house in the woods 6 years ago and after 6 years of construction they turned it into our "summer" house, with swimming pool, a small soccer field, a few small crops, chickens and some settlements for guests. I'm from South America, so it's always summer to us, that means that we go there almost every weekend we're in the city.

Recently my parents came with the idea of moving to this house, we all liked it, but the main building of that place got only 2 bedrooms, it's been more than 10 years since me and my siblings shared bedrooms, our parents know that it would be awkward to us to start sharing again and decided to "give us a second floor" as a gift (the guest settlements I mentioned before are all kinda far from the main building and they didn't want us living there).

I know this is getting long, so here is the deal. I was the last one to know they we're going to build a second floor, when I got the news from them, I got told that I was the only one staying on the first floor because my siblings had already chosen theirs rooms. I got a little bit sad because the last time we moved the same thing happened (me ending up with the smallest and worse bedroom) but I didn't care much because I've always thought to myself that as the youngest sibling I have no rights over these things. But hey, at least I'll have my own bathroom and no need for stairs.

Now that the second floor walls are up, my siblings noticed that my old bedroom is kinda bigger than theirs. My sister already said that she's staying on the first floor with me in the other bedroom that was going to be empty (it's little smaller than mine), her room on the second floor is going to be our study room.

My brother didn't like that me as the younger brother "who's starting university life away from home" is going to get the bigger room. Now he think I should stay on his smaller bedroom on the second floor. The problem is that he only said these things to our mother, not to me. He asked her to convince me. He already spoke to her twice and mom said to him that it's up to me to decide. 

Today after he talked with our mother about this again (this was the second time), he came home mad (silent mad, didn't say hi or anything to me). Just went to my bedroom (I was at the kitchen) and took his laptop from my table and took to his bedroom (he's not using it lately so he's letting me use it because my desktop stopped working), It was on and I was using it, but didn't said a thing because it is not mine (I didn't know why he was mad at that time). Later in the night he went to our close mutual friends' house (they were at our pool house yesterday and it was such a cool day because we didn't hang with them in months) without telling me or my sister, he just told our mother (who told us hours after he left). Now he's going to sleep there. He knew that I would've accepted to go there if he invited me, but he didn't invite and he probably said to our friends that I didn't want to go. 

Now I'm feeling bad. I love my brother, our bond is so strong and he is my best friend. I am thinking about giving my bedroom to him because of this but at the same time I always wanted a good large bedroom to decorate and such (his actual big bedroom is a mess because he doesn't care about it). I didn't like his atittude today and I didn't like that he and my sister didn't give a f**k about me when picking the bedrooms from the construction blueprint (they even made fun of me because I'm staying on the old bedroom). I also thought about him living in the bedroom while I'm at the Uni (I'll probably stay there for more 3 or 4 years). Anyway, AITA? 

Well, I didn't think this boring WPP would get that long, sorry! 