Yeats Howard's show of action was so swift that Marcus Quinn couldn't stop him. Instead, the Howard Family matriarch received the call, paused for a moment, and then smiled, "Is Marcus's grandson getting married? No wonder your dad whipped you with a belt last night; pass the phone to Marcus."
The matriarch did not respond to Yeats's latter words. Yeats has always had a rough character and, because of his father's influence, sees Marcus as a foster brother. This naturally leads him to have a touch of heroism and a desire to fight for Marcus. The matriarch knows this well and doesn't blame him for meddling in others' affairs.
Marcus himself hasn't turned against his father. Our Howard Family can't be the bad guys imposing on the Duncan Family. The matter of father-son relationships in this world is a convoluted affair.
