Re: TNG: The Body Electric by David Mack Review Thread (Spoilers!)
Data is definitely carrying Lal's memories, it was mentioned a couple of times.
Data himself also is not sure that he is the same person as he used to be; he expresses doubt to Geordi several times. It makes perfect sense to me that he would want Lal back, not just copied, if he's worried about his own copying.
Data is also carrying Soongs memories.
Soong 2.0 could put in an appearance just like Data...
I don't know if there is a copy of Rhea's memories.
Soon oh soon the light, Pass within and soothe this endless night, And wait here for you, Our reason to be here...