I don’t recognize my brother anymore

We’re currently in our teens. He’s a high school student, and I’m in college.I used to be super close with my brother. He used to be really funny. He loved to perform dances and trusted only me to record his “music videos.” He was all around very sweet and a good kid. After he hit 7th (ish) grade, I noticed a change.He wanted to be alone more, which is fine. He wore headphones all the time too with the volume all the way up. I absolutely cannot stand leaking sound from headphones, so I’d remind him every time. He also started changing mood really quickly—happy and kind to angry and rude... but he’s been like that forever. In his middle school years, he was honestly pretty ok still.He started high school last year, and that’s when he really started to change. He became a lot more cocky and never wanted to acknowledge me. He also went through a massive “glow up.” He used to be a fat kid but lost a lot of weight in the course of a year and shot up in height. He became physically stronger than me and used it to intimidate me. He stopped listening to my parents and rebelled a ton. He was still very tolerable.In quarantine, he’s become incredibly intolerable. His new hobby is apparently mocking me. He makes fun of my apparently high work ethic. He also enjoys picking on my slow response to sarcasm and sensitivity... His mood changes a lot too. He can go from kind to a shithead in a matter of minutes. It seems as though he’s always pissed off at something. He’s been skipping classes too, trying to at least, which causes him to fight with my parents often.He’s also been into dieting lately. His habits are similar to those of eating disorders, really. He’s become obsessed with losing weight, and it really sucks. But he’s been snappy and rude since before he started dieting.Maybe it’s just teenage hormones or maybe he has issues? I don’t know. I can’t leave home until next year (corona canceled college). I’m losing my fucking mind. We’re always fighting; it sucks. I’ve confronted my mom about it, but she denies his behavior, even though she fights with him the most.My dad and uncle don’t have a great relationship... due to my uncle’s cockiness (similar to my brother’s). My dad has another brother though. I only have one (sibling). I want to have a good relationship with him and stay friends in adulthood. Please please help me! Is this just a phase of his life or an underlying issue? Or am I just crazy? via /r/relationship_advice https://ift.tt/36v2651