At 13, you shouldn't be comparing yourself in any way to adults .. And certainly not to adult males!! Talk to your Mom about this. We just don't know you or your medical or emotional history.
I'm 13 and I'm only 5 feet tall but weigh 105. I never used to worry about it, but my sister who is 23 looks a lot thinner than me. So does her 6"3 husband. My thighs are about twice the size of his, and he's in the army so he's got muscle?