God ????'s

Lately my kids have been asking a lot of questions about God. Mostly Caleb and Grace.

 Like, "who are God's parents?", and "when is God's birthday?"

I answer, "well, God does not have a birthday because He has always been here".

I guess I have never thought of this before.  But, this must be s hard thing for them to understand.  Do any of you know if a good book that may talk about this topic?
I think all these questions are coming because we just celebrated Jesus's birthday and they know that Jesus had earthly parents and know where He was born and etc.

So, the other night I'm telling Ernie what they have been asking about and Grace was there with us and she ask him,"When is God's birthday?"  Ernie tells her the same thing, "God has always been here since the beginning"  Grace's reply "You mean He has been here even in the 80's"  HAHAHAHA!!!  Ernie says,'NICE, real NICE!"  Oh, my what the things they say.