Ethan Hawke admits raising children after divorce can be tough.

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 put these rules into a new book, ‘Rules for a Knight’, which Ethan wrote and Ryan illustrated.