The Tanner Fongs are located in the Southern half of the Merchant District, in between the entrances to Black Leopard School and the Golden Way. When you reach the house, you'll discover that the Elder Tanner Fong was never really dead; his son had just carted him off to the graveyard while he was asleep. The younger Fong will ask the player to kill his old man so that he can take over the business.
If the Player is a follower of the Way of the Open Palm, he/she can attempt to broker a reconciliation between the two. If the Player is a follower of the Way of the Closed Fist, then he/she can either agree to kill the Elder Fong or bring him outside to speak to his son, then dispose of them both.