I'm going to hazard a guess here, with it being plural, that it might be referring to both
Dougie Gray and Davie Gray.
Having been virtually an ever present in the Rangers side for 20 Years (1925-45).
The start of the 1945-45 campaign saw Dougie Gray being phased out of the team, and replaced by Davie Gray at Right Back, a player we signed from Lochee Harp.
Dougie Gray played in 9 games that season, all in the first half of the campaign, with Davie Gray coming into the side in October, and registering 27 appearances that season, all at Right Back.
The following season 1946-47 Dougie Gray made only 2 appearances (both in the Glasgow Cup), and Davie Gray got 12 appearances (in our opening 13 League and League Cup ties), playing his last game on Oct 5th. Thereafter, it was George Young who would occupy that Right Back slot.
Although both Dougie and Davie Gray were at Ibrox together for those two seasons, they were never in the same side.
Davie Gray went on to have a decent career in England, first with Preston North End (1947-48)
(pictured below, directly behind Bill Shankly), and then onto Blackburn Rovers where he made over 200 appearances for them, between 1948-53.