When you know someone and like that person, he or she is considered a peer.

This isn't necessarily the case. We might dislike someone and know them and we would still have to consider them as a peer because our peers are usually people of our age group who are in the same social situation as are we. For example a 16 year old high school student would find his peers in the same age group of high school students. And similarly for other peer groups that can be found.