Spinks is probably the most successful of a former champs sons. However, Leon isn't exactly an all time great (which makes this question difficult). Not his son so doesn't count for this question, but Johnny Saxton's great nephew (if I'm remembering this right) is Zab Judah
I know that Ad Wolgast was a patient at Patton State Hospital in San Bernardino County, California beginning in the late 1920s before being moved to the Camarillo State Hospital in Ventura County, California, where he was for the rest of his life. However, I don't know if he was a patient in Northern California. - Chuck Johnston
He was Stockton State Hospital in I think 1926 ,Before that he had a nervous breakdown and was in a hospital then he escaped and lived in the mountains for a while. He lived off the land as he was a mountain man and used to train for fights in the mountains ... During this time, I think he communicated with letters to family. And at some point Jack Doyle took care of him ,,
I think Wolgast was in and out of various hospitals for a long time ... Here's and article I saved https://www.boxingnewsonline.net/the-true-story-of-the-boxer-and-the-goat/
You are probably right that Leon's overall career falls short of the ATG label but for me being a guy that grew up in St Louis he was. That Olympic Gold medal and heavyweight title win over an aging Ali meant a lot to fighters from my town. He certainly had the talent to be so much more had his vices not sidetracked him.
Guty Espadas and his son, Jr, were both world champions. Bob Fitzsimmons and Marcel Cerdan had sons who were world ranked (top-10 by The Ring). Victor Galindez had a son, Dario, who once challenged for the WBO middleweight title.
He was ranked #8 at heavyweight in 1925. The Ring Magazine's Annual Ratings: Heavyweight--1920s - BoxRec
I know he isn't an all time great, but former welterweight lower-tier contender Floyd Mayweather apparently had a son, also named Floyd, who won a belt or two.