Before joining SVU as a Captain, Don lost Marge. She was in Florida when her plane crashed. Don was cleaning their neglected swimming pool when he got the news. Don took Marge's death hard while being in AA recovery alcoholic. He rarely went home, keeping a bed cot in his office.
In 2011, Don went undercover for a mail-order bride and, in secret for a year, hired a few escorts for company (no sex involved). The following year, Don woke up to find a dead woman with her throat cut. He was suspended while being investigated for murder. His SVU Detectives proved that Don was innocent and framed.
By 2013, Don started to see Eileen Switzer and brought her over to Olivia and Brian's dinner party. She bought over the wine for the party. Don announced that Olivia passed her Sergeant's exam, proud of her. Don took Eileen to another dinner party hosted by Olivia who was allowed to stay on with SVU rather than transferring to another unit to be a Sergeant. He put Olivia in charge in the unit so that he could retire so that Don and Eileen could go on their 6-month cruise around the world.
The Blue Wall
*In Law & Order, Don once mentioned that he had a teenage daughter.
Amaro's One Eighty