Dear Ms. Huber,
Thank you for posting your request on History Hub!
His next of kin may have been listed in his burial case file. Burial case files for WWI are in the custody of the National Archives at St. Louis (RL-SL), P.O. Box 38757, St. Louis, MO 63138-1002. For access to these records, please contact RL-SL via email at firstname.lastname@example.org. Please note that this file would not contain current information about his next of kin or their descendants.
We searched online and located an entry in the American Battle Monuments Commission’s database for Private First Class Garrett Leeker, buried in the Meuse-Argonne American Cemetery, who served in the 38th Infantry Regiment, 3rd Division, and entered service from New Jersey. His citation for the Distinguished Service Cross is posted to the Hall of Valor Project.
We searched the National Archives Catalog and located a series titled Lists of Outgoing Passengers, 1917 - 1938 in the Records of the Office of the Quartermaster General (Record Group 92). These records have not been digitized in the Catalog and are in the custody of the National Archives at College Park - Textual Reference (RDT2) and may be contacted via email at email@example.com. These records also are available through Fold3 as the collection US Army WWI Transport Service, Passenger Lists. There is an entry for Leeker, Garret V. Service Number 550897, of Company F, 38th Infantry, who sailed from the Port of Hoboken, New Jersey, on the USS Mount Vernon. The date of sailing was March 29, 1918. His wife, Mrs. Sadie Leeker, is listed as his emergency contact, with the address of 367 Virgin Ave., Jersey City, N.J. This may be an error, as there is (at present) no Virgin Avenue in Jersey City.
We searched the Catalog and located a series titled Draft Registration Cards, 1917 - 1918 in the Records of the Selective Service System (World War I) (Record Group 163). Digital images of all the records have not been added to the Catalog. For access to the original records, please contact the National Archives at Atlanta (RE-AT) via email at firstname.lastname@example.org.
We searched Ancestry and Fold3 and located an entry for Garrett Leeker, born August 7th, 1894 and living at 367 Bergen Avenue, Jersey City, New Jersey. He lists himself as married, however, no names of relatives are given. We also located draft registration cards for Charles B. Leeker (born January 1, 1897) and William Herman Leeker (born February 18, 1892) both of whom were living at the same address as Garrett Leeker. Both list themselves as single. Charles lists Edith Leeker as his Mother, with the same address.
We searched the Catalog and located the series titled Records Relating to Pilgrimages of Gold Star Mothers and Widows, 1930 - 1933 in Record Group 92. Digital images of these records are not available in the Catalog. For access to the original records, please contact the National Archives at College Park - Textual Reference (RDT2) via email at email@example.com. We searched Ancestry and located an entry for Edith Leeker, mother of Garrett Leeker of Company F, 38th Infantry, on the “List of Mothers and Widows of American Soldiers, Sailors, and Marines Entitled to Make a Pilgrimage to War Cemeteries in Europe”.
Also in Ancestry, Garrett Leeker also is listed in the New Jersey State Census for 1915 living at 367 Bergen Avenue, Jersey City, New Jersey with William H Leeker (age 55), Edith Leeker (age 50), William H. Leeker (age 24), Charles B. Leeker (age 18), Marie E. Leeker (age 15), and Edward J. Leeker (age 11).
It may be possible to find other records related to these individuals through Ancestry and similar genealogical services. However the closer you get to the present, the fewer records will be available because of privacy concerns. Ancestry and Fold3 may be accessed for free at any National Archives location. Some libraries also make it available to their patrons.
We hope this information is helpful. Best of luck with your family research!
I just looked at Garrett Leeker's grave site on Findagrave.com Someone has left a copy of his obituary on the web page about a month ago. The person's name is R. J. Stillwell, you can contact R. J. Stillwell through the find a grave web page. He may know the family members that you are seeking.
Wishing you the best