Well, in my books, if a mother decides to not want her 8 1/2
year old son to
sleep in the same bed as an adult, then, the conversation with me would end there, regardless of what i thought.
The big red flag here seems to be a problem that the grandson is so adamant that he sleep with his grandpa, and for that reason i would think that running it by a child psychologist on how to aptly handle the boys frustration at not being allowed to sleep with his grandpa or accept his mother's rules.