I hope this helps you. I have gathered this info in an attempt to find some clues as to the ancestors of my Isaac GILBERT, b. ca 1802.Frankly, I suspect that your Adam is related to my Isaac, but I have only my suspicions and the following info.
"A Genealogical Index of Miami Valley Pioneers, Ohio", pg 60 (Germantown Public Library):a George Gilbert from Frederick Co, Md had 5 sons:Adam (who married Catherine Diffenbaugh), James, George (who married Catherine Wampler, and then Mary [Brown] Wampler, a widow), David, and Isaac.
"Centennial Portrait and Biographical Record of Dayton and Montgomery County" (page 1233-1234):Jeremiah Gilbert was father of some Montgomery County settlers; he had 23 children, including 14 (including an Isaac) by a second wife, ?Powell, who Jeremiah married 27 August 1793.The same book (at pages 1231-1233) states that: the original settler was Thomas Gilbert from England, settled in Md, married a German woman, and had 2 children, Jeremiah & Susan;Jeremiah received a farm from his father Thomas, m. 1779 Catherine Weaver (whose father was soldier in Revolution), later married ?Powell, and had 23 children, including George (mother was Catherine Weaver).The book implies that this George may be the father of the 5 sons mentioned in "A Genealogical Index", etc described above.However, the same book at page 1232 states that George had only 4 children: Adam, David, James, & Isaac (no George); it further states that Adam's son, Jesse, was "of remotely German ancestors, who, on coming to America, made their home in the wilderness of Frederick county, Md, where many of the family name reached distinction." [Virtually verbatim information describes Adam Gilbert, father of the above Jesse, in Drury's History of Dayton, discussed below.]
"History of City of Dayton", by Drury, vol 2, pg 755-757:Jesse Gilbert & Adam Gilbert discussed.Jesse Gilbert, s/o Adam & Catherine (Diffenbaugh) Gilbert, married Hannah (Swihart) Mullendore.
"The Family of Thomas and Elizabeth Gilbert of Frederick County, Maryland" by Audrey Gilbert, pg 328:George Gilbert had 4 children: Adam, David, James, Isaac.Adam, b. 5 Feb 1800 Frederick Co, Md, d. 1865 Md, m. Catherine Diffenbaugh.Adam & Catherine had children: Jesse, Eleanor, John, Jane, Nelson, Mary, Joshua, Julia, Louisa, Rebecca.