Basic Trope: An immature slacker raises a young distant relative. Both learn lessons.
Straight: Bob is the very definition of One of the Kids - he's very much a slacker. When he inherits his younger brother Timmy after his parents die, he learns a lot about himself through the act of being a parent.
Exaggerated: Bob is an absolute loser with nothing to offer society. When he inherits Timmy he goes from a slacker to an ideal member of society overnight.
Downplayed: Bob cleans up his act a little while raising Timmy, but is still not that good a role model.
Justified: Raising a kid forced Bob to grow up himself; he can't really expect the kid to respect him unless he acts like an adult.
Bob is a model citizen who is incredibly mature, but raising Timmy places such a strain on him that the other facets of his life start to slip up and he reverts to a childlike state.
Timmy is a problem child to his own parents; when they die, Bob proves much more capable at handling him and he whips him into shape.
Subverted: It seems that raising Timmy has no effect on Bob...
Double Subverted: ...until he has to actually discipline the boy, after which he decides to start growing up.
Timmy literally raises Bob: cooking his meals, making sure he's ready for work, driving him there, et cetera.
Averted: Bob was already fairly mature before Timmy came; that, or Timmy has no effect.
Enforced: The author was trying to construct An Aesop about responsibility and age.
Lampshaded: "I'd say I'm raising him, but I think it's the other way around".
Invoked: Bob's parents, realizing that Bob needs some motivation to stop being such a slacker, make sure that he gets the boy in case of an accident so that he'll learn how to function in society.
Defied: "I know we may want to teach Bob some life lessons, but we've got to consider Timmy's well-being. How about a different potential father?"
Discussed: "This kid who I'm about to patron is probably going to whip me into shape".
Deconstructed: After a while, it becomes evident that Bob, while ultimately good-hearted, lacks what it takes to be an effective father figure to Timmy. He loses custody of the boy, who's subsequently bounced around to foster homes.
Reconstructed: However, this spurs Bob on to dig truly deep and improve his life to the point where he can earn custody of the boy for real.