Oh this is great stuff; Fan & promo30 have the right idea's. Although the Brother Sister scenes are my favourites, it would mix it up a little with the introduction of other family members.
Nikita in her "Slutty Sister" scene has some ball busting quotes, by far the best sibling scene I've ever seen.
Get the girls to call us names more, nothing like our sisters calling us dirty perverts and f*#king sick bas#*rds as we bribe them to take their clothes off and show us their goodies.
Getting Mum involved is a fantastic idea, even if mum didn't undress and just watched her son & daughter wank off with each other, giving them both encouragement...
One last thing, making this scene NOT a lesbian show, but have two sisters unwillingly perform for their brother, we've caught them practice kissing each other after school and have threatened to tell mum unless...you know the score