You and Aegon have been betrothed since birth. Viserys was the one to arrange this.

Since you are from the Arryn House, Viserys felt it necessary for his son to marry you because he still wanted to be connected to the Arryns.

The two of you didn’t grow up together though, it was to keep the two of you from possibly making bastards.

Since you were fifteen now and would soon marry, you were brought to King’s Landing.

You were in the Grand Sept when you heard footsteps approaching.