Hiccup Horrendous Haddock III is a fifteen-year-old teenage Viking who was once was a weakling but now a hero from saving his village from a huge dragon that tried to attack his Village.
He lives with his father, Stoick the Vast who is the chief and he infact is an only child. It's a mystery that we don't see his mother in HTTYD because she might have died in a battle long ago when Hiccup was little.
All his life, Hiccup had been bullied, laugh at and disrespected by his father since he was a different Viking and didn't belong. Now that he was a hero, his life changed with everybody respecting for who he is.