Maggie had a son, Daniel Jonas (no idea as to father)
Daniel's father was George Jonas, who was Victor's close friend when they were young. George and his wife Lillian Parker Jonas were having trouble having a baby so Victor arranged to have the eggs stolen from a lab to do an in vitro procedure (even though that's obviously a re-write since that procedure didn't exist when Daniel would've been conceived/born). Maggie having her eggs frozen while young and married to Mickey was an obvious re-write, too.
Julie and Jennifer had the ornaments made for Daniel and Melanie (and eventually Parker) as a surprise after finding out they were Maggie's bio son and granddaughter. They also surprised Maggie with the ornament for Victor. Bill and Julie told Maggie she'd always be considered family, even though Mickey had died.
Laura's ornament continues to be hung on the tree even though she and Bill were divorced decades ago. Doug's ornament was still hung on the tree after he and Julie had divorced back in the day, too.
Alice didn't hold a strict blood-only policy for ornaments, not even back in the 70s when she gave one to Dougie LeClair (as Doug's godson, since no one knew Doug was Dougie's bio dad) and Janice, Mickey and Maggie's foster daughter, who was returned to her bio mother as a little girl a year or two later. They continued hanging her ornament for years. She didn't return to Salem until the late 80s as a grown woman. When Hope was the amnesiac Gina, before it was determined she was actually Hope, Alice gave her a Gina ornament.
As to former spouses (or boyfriends/girlfriends), for the most part, once they were divorced (or broken up) from the Horton family member, their ornament was never hung on the tree again; sometimes you might see a stray ex ornament in the box, but that's where it stayed. (like Bonnie, Nicole, Chloe, Sami, Carrie, Faith, Stephanie, Peter Blake, etc.) And obviously Chase's ornament was ditched after he raped Ciara. (he got an ornament as Hope's stepson, the same as Chelsea got one as Hope's stepdaughter) Johnny's ornament wasn't shown after that first year, when it was determined Lucas wasn't his father.