How can I keep the planes relatively fixed to a piece in a top down assembly ?

so i'm designing two parts to assemble them

i drew the first one ( with its own planes ) , and then the second one ( also with its own planes but this time there was a constraint between the sketch and a plane of the first design ) , the problem is that whenever i manipulate the first part to see if the second one follows , the planes of the second one remains in their absolute position , while the planes of the first one move with the first part , what can i do to have the planes of the second part move with it ?