How to rotate a rigidbody relative to another?

If you have a parent transform (no rigidbody), and a child rigidbody - when you rotate the parent, the child rigidbody rotates relative to the parent, as well as being affected by gravity and colliders etc.

In order to get around several other issues I had to move away from this setup and toward a fully physics approach, by attaching a kinematic rigidbody to the parent and using Rigidbody2D.MoveRotation instead of rotating the transform. I have unparented the child rigidbody as I know you shouldn't have rigidbodies in parent/child relationships, but I don't know how to successfully replicate the relative rotation now.

What would be the best way to achieve this?