If the events at the end of book 11 had not taken place, Snotlout would have become Hiccup's personal body guard and most loyal defender, because Camicazi would have been busy going on adventures. He would never have escaped his past, but would have spent the rest of his life making up for it.
Fishlegs never gets married but does father several children, all of whom are brought immediately and without hesitation into clan No-Name. He never quite becomes a father figure per se, but does provide faithfully and act as a mentor to all his kids once they're old enough for him to feel like they can actually talk as people with one another.
Camicazi becomes a questing hero like Valhallarama and Humungously Huge and Tantrum
By the time Hiccup's kids are toddlers, Toothless is behaving developmentally more like a 5-6 year old than a 2-4 year old like we see in the books, and so gets to enjoy both being a scaly big brother to the babies and the doted upon baby scaly brother when they outgrow him, them repeats the same pattern with Hiccup's grandchildren. By the time Hiccup has great-grandchildren though Toothless is spending more and more time away with the Windwalker and feels to them more like an occasional visitor than a member of the family.
Hiccup stays short his entire life.
Humungously Hotshot and Tantrum have no children, which is a minor disappointment but not all that important to them in the end.
Valhallarama carries genuine affection for Stoick her entire life, but also never truly moves on from her first love; there's a sense of duty and resignation about that loss that never fully goes away.
Stoick is actually very insecure, all the time, forever, and has been so since childhood. Pursuing and marrying Valhallarama made it worse, actually, because he is 1) deeply aware that he was the second choice, 2) utterly in love with her with zero reservation, and 3) conscious of the fact that being a single father to a child with an absent mother while also being The Chief is not easy and also not a situation he's willing to change because he doesn't want/feel like he can tell Valhallarama how he feels about it. He just deals. That insecurity never fully goes away, though the burden of it is eased some when Hiccup truly steps in as King and Stoick's chiefly responsibilities are lessened slightly. It's a complex thing to feel grateful for the lessened weight at the same time that you feel embarrassed that your son is in charge of you, but he does what he always gets around to eventually and humbles himself enough to take the win and be proud of his boy instead of letting it fester.
This is an alternate retelling of the story of Hiccup the First.
This is an alternate-alternate retelling of the story of Hiccup the First.
