You are not fat! 105 is normal! Don't let him say those things to you, or else you might start to believe it one day, which can lead to a lot of problems. Trust me. Love your body, and don't go by what others say about you. :)
you are not fat a average 13 year old girl should weigh is 110-115
no. when i was 13 i was the same height as you and was 125 pounds. you're more like underweight. your brother is just being mean.
105 is NOT fat. Thats underweight hun.