I see the brother and sister as being related but different - not necessarily opposites but complimentary to each other.
I love Patrick's Deviant Moon deck (because of it's unique characters - human but not, like a dream unreal). It's very graphic and symbolic and can be scary sometimes (just like life).
I ope the sister will be similar but different - expanding on each card. When creators make multiple decks, I feel they have to keep their style - take Ciro Marchetti and his three creations - the Tarot of Dreams, the Gilded Tarot, and Legacy of the Divine Tarot - they are all different but similar and all his take on the Tarot.
Can't wait to see some images!