1) I wanted to know if there are any supplications to bring unity amongst family members.
2) If siblings do not speak to each other and have issues, do the parents who have passed away have to suffer the consequences for not solving issues while they were alive?

1) Dua is a great thing but first reconciliation attempts should take priority among the siblings to resolve the dispute among them first.
2) As for the last part, no unless they caused the strife among the siblings.