Does sin befall the quarreling siblings in one household, or upon the one who sought reconciliation but was unable to achieve it, given the parents' lack of effort to resolve the ongoing dispute for eight years, and what is the correct method for reconciliation?

The Shari'ah encourages affection and harmony among Muslims, not animosity and discord. This is particularly emphasized concerning kinship ties (Arham). The Shari'ah forbids abandoning relations (tajājur) among Muslims except for a legitimate reason, especially among kin. Therefore, whoever initiates good to end a severance is better than others, and parents must strive to reconcile their children.