The three sons

A family of 5 living in an isolated farm relied on one good cow's milk as a source of income.

One day the dad wakes up and sees the cow dead in the barn. Having no source of income he hanged himself in that same barn and died.

The mom wakes up after him, sees the whole thing and goes into a coma right there and then.

Third to wake up was the oldest son. He saw the whole picture, didn't know what to do so he went to the lake down the hill to seek help. Suddenly he spots a beautiful mermaid who tells him that she knows what happened and that she will revive everyone if the he will fuck her 10 times in a row, but kill him if he fails. The son with a happy look in his eyes unzips and gets right to it. He falls just short of 9 times and the mermaid kills him.

Fourth wakes up the second son. He too spots his dad, mom and cow and runs straight to the lake. That same mermaid was waiting for him saying she will make everything back to the way it was if he fucks her 15 times, but if he fails she will kill him like his older brother. He falls just short of 12 and she kills him.

Lastly, wakes up the youngest. He sees the cow, he sees his dad and mom and he too goes straight to the lake. He spots the mermaid and she offered that everything will go to the way it was if he fucks her 20 times in a row, but if he fails he will end up like his brothers, dead. The son starts to unzip his pants and the mermaid starts laughing. And then the son says: "I have a quick question before we begin, how do I know you won't die on me after 18 times like the cow did?"

Edit: fixed a misspelling and format