Perfect step-sister catches her step-brother perving on her / trying on her clothes etc. Then blackmailing him into chastity or else she will tell parents or friends etc. 
step-brother is compelled to worship his perfect step-sister and she controls him more and more and he gets desperate for release. She teases him with the key around her neck. 
 
Could also do a part when the step-sister dresses him up as a sissy when parents are out and she plays with him and he serves/worships her at all times.
 
Videos along these lines are really hot/kinky and should do more of them. Amber would be the ideal princess imo.