A Commack couple says a Manhattan fertlity clinic made a very big blunder when the pair went there to have a child. Thomas and Nancy Andrews are suing New York Medical Services for Reproductive Medicine for botching an insemination. They say another man's sperm was used by the clinic, causing their daughter's skin to be noticeably darker than either one of them. Three different DNA tests have concluded it was not Thomas Andrews' sperm that was used to inseminate his wife's eggs. They say they love their daughter as their own, but they are "reminded of this terrible mistake each and every time we look at her; it is simplyimpossible to ignore."The suit came to light Wednesday after a judge allowed the couple to proceed with parts of their lawsuit while other parts of the suit were dismissed.