consider the great great great great grandparent of a person alive today. Let's call him Person A

according to reincarnation, Person A is off living life as another being, possibly as a human

but we also talk about ancestors watching over us, such that Person A is watching over his current living descendants

Im trying to understand the relationship here. If we say that Person A has reincarnated as another physical being and is off living another life, then how is Person A also watching over us? Isn't he busy living another life? Please let me know how I can better understand this

I have a feeling the answer is somewhere between the oneness of all things and the infinite extent of reincarnation (such that in another reality, Person A literally is you and you are Person A, etc, so Person A became infinite), but I'm unsure

Thank you