Yes, it is possible for your brother's DNA to match your daughter's DNA. Your brother and your daughter share a biological relationship as uncle and niece, which means they have a genetic connection.
DNA is inherited from parents and passed down through generations. Your daughter inherits half of her DNA from you and half from her father. Since you and your brother share some DNA from your parents, your daughter will also share a portion of DNA with her uncle.
The specific amount of shared DNA between your brother and your daughter will depend on the genetic relationship and the random process of genetic recombination during meiosis (the process of creating eggs or sperm cells). On average, an uncle and niece typically share about 25% of their DNA, but the actual percentage can vary. Some nieces may share more or less DNA with their uncles due to the random nature of inheritance.
If you are interested in exploring the genetic relationship further, you can consider using DNA testing services like ancestry DNA or 23andMe. These tests can provide more specific information about the genetic relationship between your brother and your daughter. However, it's important to remember that DNA testing should only be done with the consent of all parties involved and with a clear understanding of the potential implications of the results.