Of course their grandmother is Cloris Leachman, who years previous perfected the archetype of the kooky German lady in Mel Brooks' Young Frankenstein.
Prochnow is just one of the ringers brought in by the guys, while Cloris Leachman reaquires her wacky German accent from playing Frau Blücher in "Young Frankenstein," and she gets to let loose with a lot of swearing and nastiness that will make you glad that the guys didn't take some of her scenes even further.
The boys train by drinking dozens of beers a night, occasionally receiving advice from Grandpapa's widow, called Great Gram Gram and played by old pro Cloris Leachman in the same tone of Germanic grandeur she brought to "Young Frankenstein" years ago, when she uttered the famous line "Yes . . .
When their grandfather dies, their grandmother (Cloris Leachman, channeling her Frau Blucher from "Young Frankenstein”) gets them to take granddad's ashes back to the old country.