best explanation for an 8year old?

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whenever my son goes home with me after spending weekend with his father,he will stare at me and start to cry and embrace me for comfort. He say,"why can't the 3 of us stay in one home so I can be with both of u. when I am here with u, I miss my father, when I am there I miss u.why?" Honestly, I don't know what to tell and explain to him exactly. It is breaking my heart but what he is asking is something that can never happen. What is the best explanation for him? Thank u.