Re: "no idea why the older kids were behaving so badly" - parents often compare stories about the "terrible two" stage of childhood development.

Legends abound in my own family, of my own dreadful behaviour (in the early 1960s) when my parents took me on a flight (piston-engine propeller plane over water) at the age of two years old. In comparison (always "in comparison") my new-born baby sibling slept like an angel through it all.