Re post: Why wouldn't a dna test just say he is the dad? Anyone ever had a dna test or know about them?

Because many markers are present in large parts of the population, it's hard to say X is the father. X may have identical siblings of the same gender that would have the identical markers. They would not be excluded. Also, the grandparents would all fit into the gene pool, with most of the markers present as well. They may be excluded as wrong , as grandma wouldn't be the father, and Grandpa couldn't be the mom. Also, Mom's Dad wouldn't have markers equal to dad's markers unless very closely related. Etc.