Is it normal that my brother is attracted to me?

It is quite common for brothers to be attracted to their sisters, especially if they're both of sexual age and still living at home. Simple familiarity will breed some level of attraction. He knows what your body looks like, and is curious about that. It may make you uncomfortable, but it is not unusual.

The fact that he concealed his photos, drawings, and letters, means he knows his attraction is inappropriate, and he probably had no intention of ever sharing them with you. I confess, when I was twenty, I wrote love letters to my younger sister, which I then burned. I never, ever told her. However, the practice writing gave me the skill and freedom to express my feelings to other women, for which I remain grateful.

Please realize, your brother cannot help his feelings. Speak with him calmly, make sure he understands your boundaries, and remind him to always respect the limits a woman gives him. This could be a learning moment for your brother: what he learns from you could influence how he treats women going forward. Teach him that his feelings are private, but your boundaries are absolute. This, hopefully, will keep you safe, and make him a better person.

How old are you and your brother?

I'm wondering why you confronted him..... I mean you already had the proof.

Unless a small part of you was aroused by it...

Instincts aren't necessarily aware of social rules... Though there is some evolutionary incentive not to have offspring with close relatives due to birth defects and such, it's not very strong. Just watch a litter of kittens or puppies going through puberty who haven't had their operations yet. Same goes for how it's natural to be attracted to multiple people even if you practice faithful monogamy.

For that matter, checking out some psychology studies you'll come across stuff describing how family members can form the fundamental impressions of the world, like a person's idea of what it is to be male and female, which is a major component of later sex drives; If someone is attracted to girls, and you are fundamental to that person's early understanding of femininity, there is some potential for bleedover.

So the most important things are to not reproduce, to avoid letting loose information which could cause massively disproportionate social stigma, and to avoid giving him a hard time about what may be the most embarrassing moment of his life.

Make sure to be nice with him. Also promise him that as long as he keeps his feelings to himself that you will never tell anyone. Family members, especially siblings, should have a certain level of trust like that. Tell him that you understand but you don't share his feelings and he should find a girl who reminds him of you.