Joined rigid bodies no-collide

My problem, is that rigid bodies seem to not collide when joined by a hinge joint.

non of the rigid bodies have collides, but they have children which all have collides (not sure if that is relevant).

If I join Object A to object B, they will not collide with each other. However if I join Objects A and B to C, A and B will collide because they are not directly connected.

Is this an intended effect? is there any way to turn it off?

(sorry if my rambling is hard to follow D:)

I haven’t acutally used this, but I would say it is an intended affect, otherwise it would be hard to make a ragdoll.