I assume a male from the other family has to take the test, is that right?
Just to say, that my husband and I both have Irish heritage and looking at DNA contacts, if there is a published tree, although there are no obvious links, I can tell from the surnames which are local to our areas how the likely match has arisen. With the lack of records and emigration (I am going back to 1800s) matches cannot be made. But the DNA link is there.