What are the similarities and differences between the two families?

Callum McGregor and Persephone “Sephy” Hadley are from different worlds. She is a Cross, dark-skinned, wealthy, and privileged; he is a nought, the light-skinned lower class that was once enslaved by Crosses. Sephy’s father, Kamal, is the Home Office Minister, and she has multiple homes with servants; Callum’s parents, Meggie and Ryan, can hardly scrape by, especially after Meggie was fired by Sephy’s mother, Jasmine, three years ago. The children are forbidden from seeing each other, but for the last three years, Sephy and Callum have been secretly meeting on Sephy’s private beach. They are best friends, though Callum is very aware of the differences in their status and world views.