What is the ruling of Sharia on the continuation of severed kinship ties with maternal uncles after the death of the grandfather, and are the children considered to be severing their kinship ties despite their father's attempts at reconciliation and the grandfather's refusal of it?

The Sharia (definition) has urged harmony and affection among Muslims, especially among kinsfolk. You must maintain ties with your relatives even if they cut you off, and the sin is upon whoever severs ties. Do not despair of reconciliation, and seek help from Allah, then from virtuous and wise people to influence them, and remind them that disputes over this fleeting world are a loss in both religion and worldly life. If the dispute over the house continues, it is best to refer the matter to the Sharia court.