Triple trouble on Exile Farm.

The interesting thing about the real Cruikshank family is that they have three daughters. The other interesting fact is that they're much the same age as Kate and Aaron are. This is why whenever Cousin Laura appeared, she seemed to be just a little older than the Patterson child she was calling a clodhopper. What this tells us is that something entertaining is happening that the Patterson family are too dim to realize: Bev and Danny also have three daughters. For the sake of convenience, let's call them Karen, Laura and Melanie. They look similar enough that someone not especially familiar with their family would confuse them with one another and none of the three of them especially loved playing baby-sitter because their idiot uncle from the big city was too big of a girl's blouse to deal with the alleged out-of-control behaviour of his slug-like imbecile offspring.

This led the three of them to formulate a plan to prank the moron city folk; said plan involves their conceit that whatever 'Laura' stuck Foob-sitting is an only child. Since idiot Mike and clueless Liz are almost attentive as their moron parents, the gag is a viable one and since by the time the Martian showed up, Karen and the real Laura had moved elsewhere, it seemed appropriate to just let the idiots from the city go right on being ignorant. It should be noted that John was probably as big an asshole as an older brother as he is a father and husband so it's easy to see why Bev and Danny would get in on the fun. After all, there's nothing farm people love better than putting one over on city folk. The success of the Letters From Wingfield Farms series of plays is testament to that.