Alex is Ignoring Me

Alex is my brother and I'd like to put it in writing that he is annoying because he keeps ignoring me when I Skype him. Almost every other day I send a skype message and I never get any response. I know he's online and I know it works because I got him to test it once when I was on the phone with him. I don't know, is it really that hard to respond to a message? He doesn't have to bother with headphones, it doesn't cost him anything, it's not going to take up much of his precious time. I don't understand. He's a pain.