Estate talks w/ siblings that don't help - Who gets what?

As we get all of Mom's affairs in order, the topic was raised how to split her estate when she passes. Siblings that do nothing want an equal share while the main caregiver would rather base it on the amount of participation with Mom's care. How do we have an equitable talk w/o arguing or hating one another? It seems a bit selfish to split evenly when the majority of her care is primarily w/one child. (Our Elder Law Atty says it's up to us to agree so no real help there.) Thank to everyone that answers or offers input.