Is it permissible to bury a deceased son next to his grandmother and aunt, with a non-permanent divider between them, and is it permissible to exhume the remains for construction?

The default is to bury each deceased person in a separate grave with a lahd (niche), unless there is a necessity. Such necessities include the scarcity of burial space, soft ground, or high groundwater levels. In these cases, it is permissible to bury in built chambers and to combine more than one deceased person within them, prioritizing men over women, with an earthen barrier placed between them. It is not permissible to exhume a grave to move the deceased unless the body has not decomposed. If the body has decomposed, it is not permissible to exhume it.