Here is what I have from CWSS:

7th Regiment, Texas Cavalry (7th Mounted Volunteers)

566 Gardiner, James W. I Captain Captain

567 Gardner, James W. I Captain Captain

568 Garner, A.J. F Private Private

569 Garner, B.E. I Private Private

570 Garner, Benjamin E. I Private Private

571 Garner, H.F. I Private Private

572 Garner, J.P. I Private Sergeant

573 Garner, William A. I Private Private

Those without the d are maybe mine. I think the captain would not have gotten the spelling wrong if they were his relatives, so I would rule him out.

Johnny, I don't see any overlap on the group you list, so the mystery continues.