This could be so useful.
I don't understand what you're asking for. Are you talking about deceased relatives who were members of the Church? If so, they should almost all be in Family Tree (as long as their ward clerk marked them as deceased). If you're hoping you could use the Membership Record Number to find relatives in the Tree, I suppose that could be done, but those MRNs are not generally known, so I don't know how useful that would be. If I still don't understand and you are hoping for something else, please provide more details about how you think it should work, and why it would be useful.