There are three Keysers listed in the on-line rolls of the 17th Connecticut Volunteers, a Civil War unit that fought at Gettysburg, Chancellorville, and Fort Wagner.
Two are listed as as William R. Keyser:
1, Corporal Co, F from Norwalk, CT whose daughter Mary Emma Keyser was born 1871 and married William Scribner of Wilton in 1888 in Wilton, my great-grandfather.
2. Private, Co. E. from Weston, CT, discharged early with disability.
There is also a Private Milton Keyser, Co. F, of Wilton. All three could have been easily related as all their towns of enlistment in Fairfield County are neighboring in Connecticut within about a five to ten mile radius.