Can a trigger detect other Colliders in the same parent when the parent is the RigidBody ?

So, I have parent object (A) with a RigidBody, and it’s Colliders are all in children objects (A1,A2,A3,etc).
I also have another object with a Collider asTrigger (B) to detect if it touch any part of (A).
But as (A) is moving alot, and (B) needs to move alot too but relative to (A), I would like to set (B) as a child of (A).
Problem is, when (B) is a child of (A), it seems unable to interact with any other children.
I’m currently using OnTriggerEnter() in a script inside of (B) to detect the collision.
From what I understant (A) can’t detect collision within itself, wich make sense, but… it’s what I need so…
I would also rather not have to move & rotate (B) each fixedUpdate to follow (A), nor giving it a RigidBody component, as it isn’t supposed to interfer in the physics of other objects.

Thanks in advance for any advice!

Figured out it’s easier to just have a parent object (C) containing (A) & (B)