Who is in the wrong here??

Sorry I know there a lot of mistakes in this but i don't have time to fix them. i have to leave in like 30 seconds. I was helping my older brother who came home from college write a letter to his professor. I am Only 13 but i noticed many grammatical and word usage mistakes. So, I helped him rewrite the entire letter. (it was pretty messed up.) After I helped, he went to go show my aunt so she would approve it. When she read the letter she was very impressed and told him it was one of the most well written letters she has ever seen. My brother then said that it was all him and that he had no help whatsoever. I was insulted. Was it wrong of me to want recognition for what I did or was i wrong for him to take credit for the work that I mostly did myself?