Is one considered sinful if his relatives do not greet him due to a dispute over a plot of land, even though he initiates the greeting, and does this fall under the Hadith: "It is not permissible for a Muslim to abandon his brother for more than three (days)"?

The Hadith (definition) mentioned is authentic, and its wording is: "It is not lawful for a Muslim to abandon his brother for more than three nights. They meet, and this one turns away, and that one turns away. The better of them is the one who begins with the greeting of Salam." The questioner's greeting of Salam to his uncle and his children severs the abandonment on his part. Whoever among them does not return the Salam bears the sin of severance and abandonment. Abandonment does not prevent the acceptance of good deeds, even though it carries a warning of deprivation of forgiveness until the estranged parties reconcile.