Today, as every day, I left ds toddling about with both dds while I popped through to put their tea on (kitchen/dining room not a safe area for ds).
I come back through to find ds happily munching on crayons while dd1 is oblivious (unsurprisingly) and dd2 is glued to the tv. with the empty crayon box in her lap, where ds has emptied it 
when I remove te crayons from ds, and express irritation that dd2 has left them where he can get his hands on them (all the while fishing bits of crayon out ofnhis mouth), dd2's main concern is....?
that he hasn't eaten her favourite colour! apparently it's all ok, as she still has her favourite one to draw with. so much for empathy!
oh, hang on, she did get a bit worried that ds would be too full to eat his tea 