Brown and Gill have spent the last month on loan at Valley Parade and Bradford manager Peter Taylor was keen to keep hold of the two defenders.
Taylor said: "We would have liked to have kept them for a little longer, but we believe United need them to fulfil some reserve matches.
"It's a shame because I think they've enjoyed it. They have both done some good things for us and I think they would have got better if they'd stayed longer."
Gill, son of United chief executive David, has played in all five of the Bantams' league games since his arrival, while Brown, brother of United defender Wes, has made three appearances despite a knee injury.