I'm having a normal day about Thomas Hamilton, so here's a bunch of headcanons about his upbringing :
He's an only son ( at least legitimate ). His mother died at childbirth and in the moments in which he ponders whether his father has a soul or not, he thinks perhaps Alfred Hamilton was a different person before his wife died and that's why he hates him so much.
Instead of a loving mother, he grew up with a step mother that never cared for him very much and would've probably wished he wasn't there at all, because he was always a reminder that if she ever bore children, they would be second to him.
It was his governess the one he actually "imprinted" on. She was the one who feed his hunger for reading and made him into a dreamer, by reading him lots of fairy tales and legends and fantastical stories. His father though always saw them as useless reading until he forbid them from the house, and burned them in front of Thomas' eyes. He couldn't have been older than 8.
His first love was the stable boy in the Hamilton state. They were children playing at love more than anything, but he did gave him his first kiss. The boy and his family were out of the property a month before Thomas departed to Eton. His father never explained why he kicked them out, but if he knew, he never told.
Eton was the place he grew to know himself. Without his father breathing down his neck he realized he enjoyed debating with people and exchanging ideas and learning new things. His teachers adored him, his fellow students… not so much. Except for Peter. Peter was his best friend in the entire world.
When they went form Eton to Oxford their relationship only deepened. They probably made out once or twice while drunk, when they were first trying alcohol but Peter always made it as if nothing had happened next morning, so Thomas did as well. In any case it wasn't as if his feelings for Peter were romantic anyways.