Why have i got klinefelters and no one in my family has?

Sporadic event: Klinefelter syndrome is not influenced by heredity.During conception, the male or female should donate 1 of each chromosome pair to the egg. If the male donates his complete pair (xy) of the sex chromosome & it joins with mothers x, you set up a XXY fertile egg that grows up affected. In the same way, the mother could donate her xx & the dad his y to give the same outcome.