From an early age, Newt had known that he didn't fit in with his peers. After a certain amount of time, Newt simply stopped trying. It wasn't like the other kids were interesting, anyway. They wanted to talk about boring things, like Quidditch and dolls. Not one of them was interested in his mother's wonderful hippogriffs, or the Ashwinder that had sprung up his fireplace after they had left the Floo burning for too long.
So Newt talked to his parents, and Theseus, and his teachers. They'd all supported his interest, but Newt could talk for hours and hours about fantastic creatures, and wasn't very good at recognizing when they were getting bored. Magical beasts were fascinating, weren't they?, and how anyone could get bored hearing about them Newt couldn't even imagine.
And Newt drifted away from his classmates before he started Hogwarts. Then, he got a letter, and was shipped off by train to Scotland, where he'd meet lots of new
and interesting people. In his year, in Ravenclaw, there was a boy named Silvanus Kettleburn - who shared Newt's interest! - but his was more of an interest and less of Newt's obsession. They had several interesting conversations, but in the end, they were more acquaintances and less friends. Newt was Sorted into Hufflepuff, where he had the benefits of House-system bonding, to an extent.
Even for Hufflepuff, titled by the other Houses as the leftovers, Newt was an oddball. He was, however, fiercely loyal to his one friend, Leta Lestrange of Slytherin. Newt'd never really had a friend before (unless you count Theseus, but Newt didn't), and Leta was a surprise. He valued that relationship very highly, until The Incident in sixth year, when Newt was kicked out of Hogwarts.
With such a bad track record for friendships, Newt fell back on his creatures, which were as kind, trusting, and gentle to him as he was to them. When the war arrived, Newt was barely out of Hogwarts, but he knew he wanted to fight. He fell back on his creatures to help him get through, this time Ukranian Ironbellies - did you know that Ironbellies are the largest breed of dragon, sometimes weighing up to six tonnes? After the Great War (A/N: WWI was not called such until after WWII, because no one predicted a second) ends, though, Newt continues to rely on his creatures for emotional support. In turn, Newt saves them from traffickers around the world.
Eight years after the war ends, Newt comes across a trafficked thunderbird in Egypt - it should not have been there, thunderbirds belong in North America- and resolves then and there to return Frank to his rightful place.
In the year 1926, Newton Artemis Fido Scamander steps off a boat to New York with a case of magical creatures in one hand, a bowtruckle in his pocket, and determination singing through his blood.