I need opinions on this..?

My brother has a friend that is about 4 years older than me. Basically, we both found out that we are music soulmates and very compatible. Every time he comes over he pesters me to come listen to them play music and wants me to play with him too. He always talks about how I'm his future wife and asked my brother if that was okay, and when my brother said yes then he asked me if I would be his "girly friend." then he started talking to me on facebook everytime we are both on about how we need to get together and play soon and was liking status' about how I'm unique and not like other girls. Then I was waiting in the car for my brother (they were at another friends house) and he runs outside to talk to me in the freezing cold then invites me inside. Then later that night he tells me we need to have a "music date" and invited me to his house to play music and teach him to play the guitar. But then today he was at my house and told me his "lady friend was messaging him." but then he posted something on facebook about how age shouldn't matter and so on... so what is his deal?