Tough conversations with a 4 year old

Ryan is now at an age where he's observing the world a bit more intensely and he's understanding family relationships and dynamics.

This has brought about some tricky questions that James and I are finding a bit tough to answer. 

For instance, he now has a better understanding that he has a brother. However, the concept of death is too abstract so, he can't quite grasp why his brother isn't with us.

For James and I, that's tough to answer. We're not a religious family so it doesn't feel quite right saying he's with God or Angels or whatever believers say to their own children. However, isn't that a nicer concept for him to picture than to just say "he's not here anymore"?

Sometimes I regret having explained to him he has a brother at so tender an age. However, Nathan is a member of our family and I don't want to pretend otherwise.

But, he's been asking more and more about having a brother (or a sister, depends on the day - he tends to alternate between the two). 

I used to tell him that yes, he will have one but we're not sure when. I no longer feel comfortable answering that way. It feels more and more like a promise I'm not sure we can keep. 

So I decided to use two of his friends as examples of single child families. When he told me Tuesday he wanted a sister I told him that G doesn't have a brother or sister either (and, according to G's mom, never will). I thought maybe that would make him feel a little less alone in a classroom/playground full of friends with siblings. Then I explained his friend P doesn't have a brother or sister either (not sure of their standing on future children) and that not having a sister or brother means he doesn't have to share his toys every day and he gets all our attention to himself. 

This didn't seem to comfort him and it's brought me to tears. Last night as we were eating dinner with my Aunt, who was visiting from out of town, he said again that he wanted his brother (I don't know if that was abstract "a brother" or if he meant Nathan).

I'm ill-equipped to answer these questions. Not just because of how Ryan will take it but, also because of how much it hurts me to have to admit now that Ryan might not have another sibling (something I used to think was a foregone conclusion). 

Ouch.