ah;; it’s been a while but i’ll try!! the au was kind of based on the assumption that donald, della and gladstone grew up together - somewhat canon in comic-verse if i remember correctly, but the lore gets Wild -, and that losing della took a heavy toll on both of them.it was also inspired by the “twenty dollars!” gag in gladstone’s debut episode, which made it seem like the two lived together as adults at a point. 

with donald already struggling with his mental health previously to the spear of selene incident (anxiety, military related ptsd, the whole package) and him having to become an instant parent to della’s children on top of the grief, i’d imagine he was very much between a rock and a hard place. plus, with scrooge cut off, he didn’t really have anyone to turn to for help. not like that’s a thing he very often does, though, not for his own sake at least. 

gladstone’s expression of grief i feel like would be completely different - not for a lack of caring, of course -, and after checking up on donald and declaring himself the more functional of them, he decides to help him out with the kids till he finds his footing - and at the same time have him move out of the house della previously lived in because that’s just… really not a good place for anyone.  

i didn’t pan it for a long-term solution - donald can only take so much of gladstone - more of about a year or so, with donald slowly learning to accept gladstone’s offer of part-time responsibility and getting back on his feet in the meantime (getting on medication, seeing a therapist he canonically sees now, ha!), and leaving once he picked up the pieces della’s disappearence left him with. 

plus i feel like caring for someone, and especially donald and the kids would have been mutually beneficial for gladstone too, in dealing with his own grief.