The WMG Page for 'Lost Boy', one for guesses ranging from relatively simple and benign, to complex and mindscrewing.
Submit your feral and wild guesses below:
Spitelout was in on Hiccup's kidnapping and that Valka was possibly murdered.
Spitelout's irrational hatred of Hiccup from the moment they meet makes no sense unless he had arranged for the midwife to kill Valka and kidnap Hiccup so that Snotlout would be next in line to be chief.