The ending episode hook for the season or possibly series long mystery creates a pretty obvious reason for the falling out between Donald and Scrooge. The triplet's mother being part of an adventuring team with her uncle Scrooge and her brother(?) Donald. Some time after the boys were born Scrooge pushed them to go on…

Eyeball: "What are these long squishy tubes coming out of your gem hole?"

Greg: "Oh geez, do Steven and Connie have to be here for this I don't feel they are ready for the… you know the birds and the bees talk."