Perfect sister catches her brother perving on her / trying on her clothes etc. Then blackmailing him into chastity or else she will tell parents or friends etc. 
Brother is forced to worship his perfect 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 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.