Uh, Liam sea cow

Do you know what the best thing about being the youngest of 5 children is?
When they all inevitably die before you, you have the opportunity (some would say privilege) to ruin their reputations for all eternity. AND, get this, they aren't around to defend themselves!
You are the last remaining person who knew them before they met spouses, had children etc. You are credited with knowing them as closely as anyone really could. And this gives you a tremendous amount of leverage over them while they are still living.


Take for example this question, "How would you like your kids to remember you?"

Presumably, most people would answer along the lines of "An excellent parent, a nice human being, someone who wasn't criminally insane."

This is where you casually say, "Oh, so you wouldn't want them to know that you poisoned the puppy I got for my 13th birthday?"

They might reply, "You never had a puppy." Whether or not this is the case is completely irrelevant.

Which is why you would then say "Buy me a house and they'll never have to know what a puppy murdering sack of crap their father/mother was."

The true beauty of this plan however, can also be its greatest flaw: It's notoriously easy to poison the minds of children. Say it with me.
It's. notoriously. easy. to. poison. the. minds. of. children.
Say for example you try extorting a family member who has young children... around 5 - 9. At this larval stage in a child's life, anything the parent says tends to stick. So, if their parents mention that you, their uncle/auntie, is a liar and that no store should ever be placed in anything you say, you have just ruined the game.
Instead, you should start when the children are around their teen years. Not only will teens take no notice of anything their parents say, but more often than not will be eager to accept their parents sordid past.

Furthermore, by the time all your siblings are well and truly dead, old age should have bestowed you with a certain amount of credibility amongst the general public. Old enough to be endearing yet persuasive. But not rambly enough to sound like Grandpa Simpson. There's a fine line, so practice in front of the mirror or something.