The duo were set to join the Blades on a season-long loan which went about on transfer deadline day but it has come to the fore that the two 'Ges youngsters were not registered with the Football League in time and they will now return to Ibrox.
"It has been a very frustrating time for all concerned," Sheffield United director Scott McCabe told the club's official website.
"Everyone in the football administration team at the club has worked very hard to try and make these transfers happen, but we have had to eventually admit defeat.
"We had expected the transfers to go through and were surprised when we were told they had not been completed in time.
"The manager will now move on to other targets. It is the case that transfers can break down for many reasons, so Danny [Wilson] will already have in mind other options to strengthen our squad."