So, here's the history:
Pitch is the guardian/incarnation of the fear, nightmares and stuff, but also is a overprotective father. His son, Hiccup, will grow up until the Man In The Moon chose him to be a guardian or whatever. Something that can happen later or never, idk. Because of it, Hiccup will get older, and Pitch doesn't want see his precious little baby became an adult and then, die
In the other side of the history, we have Elsa, that is the incarnation of the Moon itself (not like Manny, that is someone completely different, it's more like Yue from "Avatar: The Last Airbender" or that song "Hijo De La Luna") and a super-overprotective mother. Her son, Jack, it's more like "whatever, just wanna grow up soon" and have his sister, Emma, that will die years later 'cuz Manny choosed just him to be a guardian (sorry for that).
So years later, Jack and Hiccup move on to another city, meet each other (even that the video don't show it) and remember their childhood moments and how their parents loved (and still love) they. Then, both started to wish that they never had grew up (Jack u lil shit) and don't want to grow up anymore (in that case, just Hiccup, because Manny is being a douchebag and still doesn't choose Hiccup to be a Dragon Guardian. Manny, you suck)
So, that's it! I hope you guys enjoy
Non of thouse movies (or that awasome music) belongs to me. The song "Never Grow Up" belongs to Taylor Swift and the movies belongs to DreamWorks, Disney and llumination Entertainment.
Pitch Black: Hiccup's father (the fear)
Elsa: Jack's mother (the moon)
Jack Frost: The winter guardian and all that stuff
Hiccup: A viking son od the fear
Toothless: A birthday gift
Jamie Bennett: Young Hiccup
Ted Wiggins: Young Jack
Jackson Overland: Normal Jack
Older!Hiccup: Well... The older... Hiccup (?)