In ongoing canons (such as TV shows that are still running) someone could start writing a fic during season three and make up a backstory for the characters that is later, say in season six, shown to contradict canon. It seems unfair to charge for contradicting canon (without claiming AU) in that case.

But what about when the canon fact (say, a previous marriage) was revealed in season three and the story (with the clashing backstory; say, a child conceived with someone not the wife at that time) was first posted three weeks later? It's possible the author wrote the story before the canon fact was revealed and decided not to rewrite to fit in the canon fact. In the case I'm thinking of the author did not acknowledge canon fact took place and chose to ignore it. (Author is from the USA, as is the TV show, so I find it likely she saw the episode on its original air date).

I'd like some opinions on this matter: because the author could have known the character was married at the time the child was conceived, should the child (who is a Sue without question) then be charged with making the character who is her father cheat on his wife? Character has been shown to be serial monogamous.