Clifford is never one to take a back seat to the action. He wants to kill York and his supporters in the very first scene—in the middle of parliament, no less. We'd like to point out that he calls these people "the family of York." He could have said "supporters," and he could have name-called (since he is not above that), but instead he points out the family relationship here. This is a family: fathers, sons, and brothers, fighting together, against another family of husband, wife, and child.