Reference your two posts regarding Kwaak.It appears that the Kwaak clan in New York is based in Brooklyn and radiates outward onto Long Island.This is a very normal suburban migration in the NYC area.I would have to believe that anyone named Kwaak on Long Island is related to the vet you are seeking information on.
The earliest casualty data you will probably find on Kwaak would be in the Casualty Lists which ran in the New York Times three to four times weekly.These are divided by state, theatre of operations and Service.Also there are lists for wounded and KIA.There is no standard as to when a particular casualty would be listed--I found one 6JUN44 KIA listd on 21OCT44.So it is matter of patience and determination, to search the lists til you find him.What it will tell you is most likely the names of his parents and their address.
Most libraries that have the NYT on microfilm have indexes which list the Casualty lists so you know exactly which Volume/pages/date to search.
A sub search for Joan Kwaak revealed one in Sarasota, FL age 73--so probably not the daughter you are seeking.The other was a Joan age 35 in Middle Village, NY which is just about in the heart of Brooklyn--no phone listed.Try the other Kwaaks on "Lon Gi-land" and you'll probably get a hit.
T/5 Clinton C. Kwaak 12056671 is listed on page 53 of the KINGS COUNTY Roll of Honor at NARA.Kings County is Brooklyn.The notation indicates that he DOW (Died of Wounds).