Personality disorder?

So throughout my brothers life I feel like he’s had some weird personality or identity issues. He’ll tell strangers he’s all these different ethnicities, he’ll go on language learning apps and spend hours among hours on them, and he’ll talk to us in that language like he doesn’t know English.. he’ll listen to songs in other languages (which I think it’s pretty cool, but...) he’ll become obsessed with them, and whatever country that singer is from, he’ll tell people and let himself believe he is ethnic to that country and language. Example, he told all his friends and strangers that him and his family are from Albania when we are not.. he’s also told people he can speak Arabic which he can from the language apps which I think is great but he’s using them inappropriately by claiming the language and culture as his own when it isn’t, but he’s learned it because he thinks he’s Arab, also. He has told other people that he’s Russian, and spoke russian to people. (Learned by apps)

He is also very paranoid about things like restaurants and other people. If he likes how someone else lives or acts, he will act and try to live the exact same way, and try to have the same opinions as that person. He won’t eat food anyone makes for him unless he makes it himself because he believes everyone wants to poison him. When we’d walk to school together he would sometimes run ahead of me or constantly look back because someone would be following us, when no one was there.

Sometimes, I’ll see him listening to music and he’ll be moving his arms around and making weird facial expressions like he’s in a music video or something. Example, he’ll be laying down listening to music and all of a sudden he’ll shoot up and start making weird facial expressions like he’d mimicking what the singer is singing and feeling. He will also get up randomly and start pacing around back and forth, sometimes he’ll play music and pace around for 2-3 hours long. And when he’s done I’ll ask him how come he did all of that and he won’t really have any recognition of it besides the pacing .. He’s 18 years old, and this has been going on since he was 13 or 14. He seems very normal besides when he does stuff like this. He’s had scans of his brain from

When he had a concussion and I’d assume everything looked normal because otherwise would have been said, so we can rule out brain trauma/ masses and stuff like that. I try being very understanding because i don’t think he realizes he has an issue.