Your royal family had been fighting with a tribe over land, your father and the leader of the tribe came to a final agreement. To marry off their first born son and daughter so they will procreate and conjoin the two rivals. One tiny, little, itsy bitsy detail was left out though. You were a male.
Your father, the king, purposely left that detail out. He knew that if he admitted to his first born, and only child, was a boy, everything would go wrong.
So your father dressed you up like a girl and it worked, he managed to deceive the tribe. He sent you off to the leaders son, Mace. He was a big, strong man. He clearly worked out. He worse a gold metal mask to hide his face and had interesting tribal marks on his biceps and parts of his chest and back.
"So, princess, about this wedding thing..." He crosses his beefy arms over his chest and looked you up and down.