First of all; define fandom.
Fandom means being in the state or condition of being a fan of someone or something.
It is in human nature to percept what they do as part of who they are. When a person becomes a fan, it's what they do, as so; it becomes who they are. Whatmore with the latest technology that shapes your perception of who you are, they can easily search a fandom and be into it until it will be who they are.
A fandom can also define a person if the person is a true fangirl/boy. Usually, these types of people are over doing their love for their fandom, that they refuse to face reality. Like that, you'll be living in your fandom. Even if you force the person out of it, it is only by the person's will that they can come out. Otherwise, they're almost dead to the world.
Understand me now, I'm not saying fandoms are bad; I'm simply highlighting the fact that if a person is too carried away in a certain fandom(s), they can lose meaning of who they are and be shaped based on the principles of their fandom.
So yes, fandom do define one's self.
This definition is not a strict one, nor is it all-encompassing. But people are not as separate or individual as they believe. They are shaped by the perceptions of others, and the way they want to be perceived. Certainly there is room for choice within this reality, but without a doubt, fans, friends, and family, all exert influences which define us.
People will never define an individual. Only the individual can define themselves. People's perception of that person may define how history looks at them. That does not mean histories perception of them is accurate. Fandom is just a bunch of people who like what the person does from the outside looking in. The people who are closest to that person are probably the only ones who truly know how to define that person.
I personally disagree, A person's fandom doesn't necessarily define the person that they are. For example, I can take two very different people who woman swoon over. One is Justin Timberlake, the other is Bill Maher. Justin Timberlake is a good-looking performer and entertainer, while Bill Maher is an intellectual and comedian that looks like an animated gargoyle.
A persons fandom does not in any way define who they are. Many celebrities and other people that follow celebrities would have you believe that their value is determined by their fandom level. But their lives are never happy no matter how high their fandom level is. It is all superficial.
A person's fandom doesn't necessarily define the person that they are. For example, I can take two very different people who woman swoon over. One is Justin Timberlake, the other is Bill Maher. Justin Timberlake is a good-looking performer and entertainer, while Bill Maher is an intellectual and comedian that looks like an animated gargoyle.