My brothers getting married and I feel wronged by him?

My brother is getting married in the spring of next year. The wedding party consists of the maid-of-honor, best man, two groomsmen and two bridesmaids. Nobody in his family is in the wedding party. Including my older brother nor myself. However, his fiancees brother, cousin and sister-in-law are all in the party. I told my mom that I did not want to hear about the wedding party because nobody in my family was represented. She thinks I am being a brat. However, I feel that I am justified. What do you think?