It is not unusual for Jews to hide their identity, especially if they can "pass." Eventually, through DNA tests, their children and grandchildren may uncover their secret Jewish family members. However, it is important to keep in mind that Jews are not a race. Jews are a people, and being Jewish implies certain cultural values as well as a shared history. If the values and history are not passed down, the identity ceases. What is most important is not the DNA connection, but to discover why the identity was hidden in the first place. (I am personally familiar with this phenomenon. When I was living in Latin America, I "passed." It was simply a matter of self-preservation.)