#mortality

My 4yo is very concerned with mortality. How can I help him understand and feel at ease?

My overly curious, smart, and big feeling 4-yr-old is connecting the dots too quickly (beyond what I think others would consider “age appropriate” contemplations or discussions) on mortality.
A combination of factors seem to be creating a heartbreaking realization in him that every once in a while, always in the still cuddle moments before bed, have him asking questions (with voice breaking, bottom lip quivering, and eyes swelling with tears) like:
“Mom, can we be together forever?”
“Can we ask God to please let us live on Earth together forever?”
“Is one of us going to go to Heaven before the other one does?”