Jasper Pride
Jasper Pride is the third child and second son of Ferry and Rufus Pride. He grew up with his older brother and sister (Stanley and Anna) and his younger sister (Sophie) on the estate at Ytene. Rufus has been head of stables for Geoffrey Carillon since the early 1920s.
Like his siblings, Jasper is amazing on and with a horse, helping his father with training and various other stable tasks from quite an early age.
He attends Schola, starting in 1945 with Rosalba Carillon, who he's been good friends with since they were both tiny. (It's not just proximity, she's nearly as good as he is on a horse.)
He joins one of the secret societies in his second year. (Spoilers! Click through for which one.)

Children