Wedding Lotto

From hitched.co.uk:

A man was surprised to hear from an old school friend of his asking if he would be the best man at his soon to be held wedding. They had not seen each other for a while and he did not really know that much about the bridegroom to be, all he remembered about him from school was that he was a great practical joker. With this in mind on the day of the wedding the best man got hold of the bridegrooms lottery ticket and noted down the numbers. As he was starting his best mans speech he said that he as well as many others followed the lottery and if no-one minded he was going to read out the winning numbers which had been called a few minutes ago, everyone duly took out their tickets checking the numbers as he called them out. He could see the bridegroom becoming more and more excited as he read out the numbers until at the end, up jumped the bridegroom yelling out that he won the lottery, he was rich, he ran round showing the ticket to all. His new bride said how wonderful as they were now rich, what do you mean we, laughed the bridegroom? This is my ticket!! I am rich, besides which I have been sleeping with your sister for the last two months, so saying he grabbed the sisters hand and left never to be seen again.