While I wouldn't trust the results without checking them by eye (or expect all cases to be found) DIFFERENCE can be used as a quick and dirty way of identifying a short list of possible duplicate records.
SELECT P1.*, P2.*
FROM People AS P1
INNER JOIN People AS P2
ON P1.Date_of_Birth = P2.Date_of_Birth
AND P1.Last_Name = P2.Last_Name
WHERE P1.Person_ID <> P2.Person_ID
AND DIFFERENCE(P1.First_Name,P2.First_Name) = 4
Fuzzy grouping through SSIS is a lot more sophisticated but the above query (or variants swapping first and last name) will give a quick idea of what you're facing very quickly.