Divorced, how to explain to toddler

I been divorced for a while.
My daughter was 2 and my son was nearly due when we separated.
My daughter now ask why we don't live with Daddy.
He moved far away and they only see him maybe twice a year.
My son obviously isn't as concerned as he never knew a life with him.
My daughter is young but still ask questions.
How do I answer them?
Does anyone have experience or advice?
This happened a while ago.
Maybe 2 years. So we been apart for a while but she still remembers and ask why we're not together.
I'm dating a new man who is great. He's met them but on a friendship standpoint as of now.
I just want to go about it in the smartest way possible.
I know they're you and may not remember but I still believe that an early impact, is an impact and will grow with them emotionally wether they remember the words spoken or not.
Just trying to be smart.
Thanks in advance.