Were the symptoms that appeared on my father, may God have mercy on him—such as psychological illnesses, claiming insects were coming out of his mouth, and knee pain—due to the presence of a grave inside the house? And must the family leave the house, or is there another solution, given the unavailability of alternative housing in the area?

One cannot be certain about the cause of the father's death. As for the discovered grave: If the interred remains have disintegrated and the earth has consumed the bones, it is permissible to utilize the grave's location for construction or other purposes, provided it is not an endowment (waqf). However, if any trace of the deceased remains, it is not permissible to build over it, walk on it, or sit on it. Accordingly, there is no impediment to dwelling in the house and building if the grave has disintegrated. If it has not disintegrated, it is permissible to build around it, provided the place was not originally a graveyard, while leaving the grave as it is and preserving its sanctity by not building over it or sitting on it.