There are various DNA tests you can have done. Grandpaternity, Infidelity, maternity, paternity, prenatal paternity, and siblingship. This is the breakdown of the different tests that can be administered.
Grandpaternity: This test compares the DNA from a child to his/her biological mother, as well as at least one of the biological paternal grandparents. Since the father would have inherited 1/2 of his DNA from his mother, and 1/2 from his father, it is preferable to include both biological grandparents in this test.
Infidelity: This test compares DNA that is extracted from an item that has been submitted to a known sample. The two are then compared to see if there is a match. This is usually used if you suspect a spouse of infidelity. Although the results are not admissible in a court trial, it will give you peace of mind.
Maternity: This test is used to determine the probability of maternity by comparing the DNA from the child to that of the alleged mother.
Paternity: This test is used to determine the probability of paternity by comparison of the DNA of the child to that of the alleged father.
Prenatal Paternity: This test is administered when waiting for determination of the biological father of the child is not an option. It is a non-invasive test that poses no risk to the unborn child and can be determined as early as 9 weeks of pregnancy.
Siblingship: This test compares the DNA from a shared biological mother to that of the sibling in question, and one or more known full or half-siblings to determine the likelihood that the unknown sibling is a full, or half-sibling, or unrelated.