I'd look into how to discuss why mommy and daddy don't live together by age ranges for such a discussion. Sometimes a simple 'daddy misses you, too' is suffice. Two of my three don't remember a before divorce life, so they have randomly claimed at 11 and 10. They were 4 and 3. My 14 year old has a choppy recollection, at best. And at this stage it's really more of a non issue as far as their feelings because they don't make it an issue. Living nearby yet seperate is their norm. Their father works many days and sees them but once a week for a couple of hours, at that. That might be something they will address internally over time. As it's on him not me.
At these ages, letting kids be kids without worrying/fretting over adult stuff is more important.