Is it permissible for a 14 year old boy to sleep in the same bed as his grandmother who is not able to sleep alone after the death of her husband?
Bismihi ta'ala
It is the etiquette of Islam that beds are not shared with someone of a different gender, whether they be related or not.
In this particular situation, it would be better to sleep in the same room, but on a different bed, or alternative options.
And Allah knows best.