This info on Ancestry, complete with a photo of Admiral Cary Travers Grayson has a different mother for him:
Admiral Cary Travers Grayson (1878-1938)
Description Son of Dr. John Cooke Grayson and Jennie Thornley Grayson, born at Salubria, the Grayson family home in Culpeper Co, Virginia. He was White House Physician to Presidents Theodore Roosevelt, William Howard Taft, and Woodrow Wilson.
Submitted by roseoftx709
Attached to Cary Travers Grayson