As the child in this situation here was my experience.
I was around 4/5 when I walked into my mum furiously throwing my dad's clothes into a suitcase. I asked what she was doing and she said "Daddy's leaving us, leaving home". I asked what she meant and she wouldn't talk further, she was so angry and upset.
I went downstairs to find my brother who was around 10 years old to seek comfort. He was playing the computer and refused to look at me, a blank expression on his face. I said "daddy's leaving? Do you know?" He replied, without breaking eye contact from his game "Yeah I know" and refused to engage with me. I can't iterate enough how out of character this was. He was and still is my best friend, a source of emotional comfort.
I then ran and hid behind a couch and cried my eyes out.
This was an awful way to find out my family was breaking up.
What I remember is feeling very alone. Nobody would tell me anything and I assume that's because I was too young.
But I needed to know it wasn't my fault, that the dad I loved dearly wasn't a demon who ran off with another woman but instead still, above all things, my dad.
They thought that by 'hiding' it from me that is somehow protected me, but it didn't, because I heard all their arguments then received no explanation other than he is going to live with another family.
So communication here is key. Which it seems like you have been doing. Communicate, in an age appropriate way, that some marriages don't work out, but mummy and daddy stay mummy and daddy even if they don't stay husband and wife.
Family therapy would have been ideal, I urge you to seek that.
Sorry this has happened to you. 