Parents of Huey, Dewey, Louie in 'Return to Xanadu'

[Mickey]

Rosa said that someone in Xanadu told the twins they would have returned
there in order to discover a secret who deals with them. Or something like
this, neither I have the story at hand. Rosa also suggested that Della and
his husband were something like Senior Woodchucks, adventurers, tomb raiders
and so on, and they might be considered "lost in mission" to justify
everything. Or something like this :)
bye

Mickey