You were the Duke's only daughter so you were arranged with the future king as his bride and as the future queen, which you didn't agree but had no other choice.

Usually, it was marriage first before the coronation but he— Sariel, decided to do the coronation before the wedding.

Before they were about to put his crown on his head, he stopped them then turned to you. "I want my wife to do it for me." He says as he looks at you expressionless.