I suppose they all sound like orphan siblings nagging and loving eachother.
The Older brother - protective and wiser;
The older sister - wild and misterious;
The middle child - the leader who gets everyone in trouble;
The younger sister(?) - a little andro-genius; And her(?) awesome sidekick, a super-smart doggy...
At least that's how I see things, not really with parenting or romance involved... Is this what you meant?