Rigidbody and Parenting - Kinematic Rigidbodies?

The manual mentions that “you should never have a parent and child rigidbody together”


Why is this?

Does this apply to a kinematic rigidbody?

If you read the page you've linked carefully you can read this ("Parenting"):

When an object is under physics control, it moves semi-independently of the way its transform parents move. If you move any parents, they will pull the Rigidbody child along with them. However, the Rigidbodies will still fall down due to gravity and react to collision events.

This applies only to normal Rigidbodies. Kinematic RBs aren't affected by any external forces.

I would assume that if you have a rigidbody the child of another rigid body, imagine a small box that is a child of a big box next to each other. and they are both effected by gravity, when they hit the floor the big box would influence the movement of the small box conflicting with the physics calculations and thus giving you unpredictable and unrealistic results.

If this is the answer then this would not apply to Kinematic Rigidbodies as their animations are not calculated.

Just my guess.