[Kizzy]

I wouldn't, you run the risk of the child 'blaming' one parent and potentially ruining their relationship with them. It's just pressure they don't need and can't or shouldn't have to understand, they're not sounding boards or emotional crutches. Also rarely do both parents have exactly the same take on the reasons for a break up, that may lead to confusion when trying to formulate an explanation.

''Psychologists have just been given a new directive which is that the age range that we work with used to be 0-18, now it's 0-25," says Antrobus.
That is also an indication that we know much more about development and that children and young people are taking much more time to develop hormonally.
We used to think things stopped a bit earlier but now we know that children's brain development is going on well into their early twenties.''

This article highlights something I've noticed for a while, that children are staying children longer mentally but not acting like children long enough.