for example
when you press shift and move the slider of lets say layer one
then both three layers speed changes.
siblings means something like "alike" i suppose but as far as I know, we have lots of casualities since b.c. 3500 on the path for the search of the meaning of siblings
sibling [sib·ling]
n. brother or sister, one who has the same parents as another person
so if you drag one of the speed sliders with the shift button down all speeds sliders will take the same position. same with the opacity sliders on the layers. move one with the shoft button down and all 3 will fade.