I have a character type too. All my characters have a similar tragic past. With the exception of CWII cast, Tod, Jul and Matty.
Alex is probably the best example had a nice childhood until around 6 when her grandfather (who she lived with) diagnosed with lung cancer and she had to watch him suffer until he died of lung cancer when she was 8. Her distance never met father died the next year. Started a new school was horribly bullied, emotionally, physically, and mentally, in school ever since. Became quite, isolated herself, was horribly socially awkward, and passively suicidal for many years until finally something happened to push her over the edge.
Same similar story for the rest of the characters.
Snapping point for Alex and Sam, was Alex's near rape
Snapping point for Ally, Laura and Pip, the end of the damn world
Snapping point for Max, Maria
Snapping point for Evy, waking up for Nesia and discovering who Matty, the boy she fell madly in love with actually was.