does love really exist?

it just came to me that when a person is normal, s/he experiences "love" when s/he feels happy around someone, and would probably like to keep that someone to her/himself to the end of her/his life, because that someone makes her/himself happy. and when that someone is gone, the person is sad.

but there are people who are not normal, and have totally no emotions about anything. they're labeled as having "anxiety". what is this state then? does it also erase love? i suppose it doesn't. and the sufferer would probably still confide his/her experience to someone s/he is close to or comfortable with. and when that someone is gone, s/he will also feel sad.

so is that also called love? how do you quantify love? when does it start and where does it end? how do you choose when there are two people you share this feeling with (doesn't it also end to who has better futures/more possessions?) ?

so, how does love exist? might it just be a sort of comfort zone?