You travel to the future and kill his children, which are the result of a timeline that you just came from (where your friend is not dead) but when you travel to the past to kill your friend, you create an alternate timeline where his children don't exist (assuming he didn't have children before you killed him).
You have the satisfaction of killing two generations, but his family only has to mourn for one generation per timeline. Also, if you tried traveling to the future from any point after you had killed him, there would be no kids to kill (assuming once again he did not have children before you killed him, and throwing out any frozen sperm nonsense).
You have the satisfaction of killing two generations, but his family only has to mourn for one generation per timeline. Also, if you tried traveling to the future from any point after you had killed him, there would be no kids to kill (assuming once again he did not have children before you killed him, and throwing out any frozen sperm nonsense).
