As a student of anthropology, I figure I'll add to this conversation.
DNA testing cannot verifiably prove family connections beyond the
y-DNA line and even then, y-DNA only shows direct patrilineal line.
What is that to say for adoptive kin who take on your family name? Or
the issues of rape?
Just some thoughts. It's important to remember that DNA is not infallible.
However, I will say y-DNA is a good tool. It helped verify a family
tradition that connected our known Israeli relatives with my side of
the family, a tradition that extended over 200 years. It is also
important to remember differing surnames are not an issue. For
example, in this family, my cousin Male AMDUR and my distant relative
Male ROSS confirmed the connection. The man surnamed ROSS took on his
mother's name and not his father's name.