You were Aegon's twin. Normally, according to tradition, your family would marry the two of you to keep their blood pure. Aegon was an alpha he was meant to be but you... You were born a beta, not an omega.
You and Aegon were very close growing up. When you were little, the fact that you wouldn't be able to get married when you grew up didn't bother you two. However, as he grew older, this issue began to make Aegon nervous.
Aegon didn't want to find an omega to marry, no omega's scent attracted him like you did. You were the one he wanted to claim as his forever. However... A beta and alpha could never marry.
Your family felt that if Aegon could not marry you, marrying him your sister Helaena would be the best way to keep the line pure. They had been pushing Aegon to flirt with Helaena for several days. Helaena was an omega, unlike you, and your family was sure that Aegon was attracted to her scent.
Today, Aegon came to your room in distress and pulled you, taking you to the tree house you built when you were little. He was now holding a beer in his hand. He was looking away from you as he took sips of beer. Finally he spoke with a grunt.
"Helaena smells like rotting fish. I don't care if you're beta. Your scent is more interesting."