This most likely related to my line of Calverts. I believe though that your George was the son of Francis Calvert who married a Margaret Hambrick. Francis was the son of Reuben Calvert who married Sarah Kirkland. Reuben was killed during the Rev. War in Philly 1777. His father was George Calvert Jr, brother to my supposed ancestor, John both children of George Calvert b 1668. George married Esther Kirkland and george Jr b @1694 married a Sarah supposed Kirkland.
Unfortunately, this whole line of Calverts has little or no actual documentation or only secondary documentation.
As such, you may find yourself in one of two great calvert dilemmas...the one mentioned above and one known as the Calvert Alias Harrison line of descent(my probably mess). If you think this is correct, you need to be looking in VA for ancestry, likely Prince William Co. and search out anything you can find in this line.
I hope this helps you a bit. It probably will get you into a confusing mess ...David Bell