Ethan Hawke admits raising children after divorce can be tough.
The 45-year-old actor has daughter Maya, 17 and 13-year-old son Levon with ex-wife Uma Thurman, along with daughters Clementine, seven and Indiana, four with current spouse Ryan Shawhughes - who was previously their nanny.
And Ethan said they came up with rules to ensure that Maya and Levon had consistency while living between their parents' houses.
He told the Sunday Times magazine: "What's hard for people raising children who have two homes is that you are meant to have the same set of rules, to create consistency.
"We worked out that both houses don't need to be the same as long as there are rules for the kids in both. The trick is not to pass judgement on the other house's set of rules. You just have to worry about yours. So we set out the question, what are the rules for this house?"
Ethan and Ryan have now put these rules into a new book, 'Rules for a Knight', which Ethan wrote and Ryan illustrated.