Relationship tests are often used instead of paternity testing. Let us say you wish to establish the paternity of a child but the alleged father cannot be tested for some reason or other. This is where relationship tests come in. By testing the DNA of the alleged father’s relatives, for example his brother, sister or parents, and comparing the DNA of one or more of his blood relatives to the DNA of the child (whose paternity is in question), we can establish whether the untested, alleged father is really the biological father of the child.