A King's Obsession - SYOC

This story will take place during Targaryen rule (set in no particular time). Peace has prospered in the Seven Realms (aside from the occasional rebellion) in large part thanks to the Targaryen/Martell marriage. However, the couple is struggling to produce a male heir, which has driven a wedge between them. This isn't helped when a young maiden comes to court and manages to catch the eye of the King. Will she change the course of history in Westeros?

This story will be centred in the crownlands, specifically King's Landing. I will need characters from the following houses:

Targaryen:

The Ruling King

Siblings of the King

Children of the King & Queen (ages ranged from 4-20 - all female).

Martell:

The Ruling Queen

Parents/siblings of the ruling Queen

Stokeworth:

The Lord/Lady of House Stokeworth

Children of House Stokeworth (one will be the daughter who catches the King's eye)

That's all I'll need to start the story. However, feel free to send in other characters. There is a character proposal form on my profile, please fill it out in order to have the character form sent to you (I need to approve your proposal first). I would prefer if the same author made the King & Queen.

This story is inspired by Torielz's Love Before Honor which never actually got fully written.