Blackness & Twinkling Lights
Inspired by House of Carter's, I wrote this for the 2006 NaNoWriMo. The character names are different, and there's only one sibling - but it was something that was working for me.
Bridget Angel has her own life, or at least, that's what she's trying to have, but she feels her life hasn't been her own since her brother became half of Double Shot, mega-band and mega-star. The other half of Double Shot, Trevor Wilson (AJ), is her boyfriend for the past four years -- drawn together after both became sober.
Zach Angel (Nick) has taken care of his sister since their parents death becomming her guardian just as he found his own freedom. He doens't mind Bridget dating his best friend, or so he thinks, until things start to change and he needs to figure out where - and when - his responsibility ends.
They discover that neither the past nor the future can change, and sorting through the 'right now' is like blackness and twinkling lights.