The Blue Demons (10-11, 2-6 in the Big East) were without senior forward Cleveland Melvin, who was suspended for a violation of team rules, and freshman guard Billy Garrett Jr., who was sick.
Coach Oliver Purnell's team hasn't won as many as three conference games in January since 2008.
DePaul was also without its best defensive player, junior guard Charles McKinney, who sprained an ankle against Xavier on Monday.
Marrero scored five points and McGhee added two points.
Young led DePaul with 23 points.
Seton Hall opened up a 59-39 lead with 12:59 to play, as the Blue Demons' last lead of the game was 4-2.
Edwin was unstoppable in the first half. Playing on the wing, he poured in 22 points to help Seton Hall to a 45-25 advantage. The 25 points were DePaul's second lowest in the first half this season.
The Blue Demons got to within 29-19 with 5:39 left in the half after guard R.J. Curington buried a 3-pointer, but fell victim to an 11-2 Seton Hall burst that moved the Pirates' lead to 40-21 with 3:28 to play.
Curington led the Blue Demons with 10 points in the half.
DePaul committed five turnovers in the first five minutes and trailed, 13-4. Edwin scored 10 points during the run.
NOTES: Seton Hall G/F Fuquan Edwin is third in the nation in steals with 45 in 14 games, a 3.21 average per game. ... Senior swingman Fuquan Edwin became the 21st Pirate to pass the 1,400-point mark when he scored 12 points at St. John's on Thursday. He is Seton Hall's all-time leader with 294. ... DePaul leads the Big East in offensive rebounding with a 13.2 average. ... The Blue Demons have been outscored in their first seven Big East games by an average of 9.3 points, the most in the conference.