Mommy... Who is God?

OH BOY! My son is something else! We're driving home from my mothers house and we start playing a game counting how many cousins he has, how many parents, how many aunts, how many grandparents... So while we're counting his grandparents he counts "Pop Pop" who is my husbands grandfather (who is no longer with us). The wild thing is that my son ALWAYS talks about him and he passed when he was just 1. Anyhoo, he says "well, pop pop is in heaven" and I say "yup" he says "Mommy, who takes care of people in heaven" I say " God takes care of people in heaven sweetie" he says "well, who is God anyway mommy?" SHEESH, he's 4! Wasn't expecting this! I say "well, God created everything around us, me, you, everything." he says "oh"... a long pause and then says "so, God is going to take care of me when I get to heaven?" I say "Yes sweetie" he BURSTS out crying and says "I want youuuuuuuuuuu to take care of me mommy!" Now I'm feeling stuck! So I say "Boopity, mommy is going to heaven before you anyway sweetie so I'll be waiting for you when you turn 100 years old" he says "noooooo mommy! I want you to stay here with meeeeeeee" YIYIYI!!!! Anything I said got this type of reaction... I then try to fix it and say " Baby, you're going to be 100 by the time you get to heaven, you'll have had a family, your own house..." he interrupts BALLING again "I don't want my own house, I want to live with youuuuuu!" At this point, I'm speechless... I just tell him that I'm going to always take care of him forever and ever.

I certainly wasn't expecting this! I try to explain things to my children (even though she's 1) the best way that I can without corrupting their little minds or treating them as if they aren't intelligent. There's such a fine line because I felt like I didn't want to take the conversation any deeper than I did. But I also didn't want to tell him fairies are going to swoop down, etc... I don't know, this boy amazes me every second... he later asked me why his cousins had different fathers and him & Little Bittle have the same father...