Can i find out if my daughter is really mine through a DNA test from her son?

No, you cannot determine if you are the father of your daughter by conducting a DNA test on her son. While DNA testing can reveal biological relationships, genetic analysis of your daughter's son will show only if he is related to you as his grandfather, not whether you are your daughter's biological father.

DNA testing for paternity involves comparing the DNA profiles of an alleged father and a purported child; testing a grandchild's DNA does not directly answer questions about biological fatherhood of their parent. To accurately establish your biological relationship with your daughter, a paternity DNA test directly involving samples from you and your daughter should be performed. A qualified DNA testing facility or authorized entity such as a court-ordered paternity test can reliably determine paternity by analyzing heritable genetic markers and comparing DNA strands.