He wants a sister

never thought I'd get pressure to have a second baby from my 3 year old.  But he has been pressing hard for a little sister for a couple of months now.  I don't think he knows what he is asking for.  When asked where we are going to get this little sister store, the response is "from the store."  Aw, no, I explain.  Mommies grow babies in their tummies so you have to wait for mommy to get a baby in her tummy.  He counters that he can just grow the baby in his tummy since it is his little sister.  Well, I response, it will be my baby so I should be the one to grow her.  Now? he asks.  No, after your aunt's wedding next year.
Wedding?  Getting married?  Who's getting married?  Are you?
No, I am already married.  Aunt Katy is going to marry Uncle John (he already calls sister-in-law's fiancé uncle, but they have been together as long as Bub has been alive).  Yeah, the concept of marriage is a hard one for a 3 year old.  That's ok, I tell him, I'll let you know when the time comes.  You can be the first to know.  So I'm hoping for a little sister which will make everyone happy, our mothers, our sisters and apparently Bub.  But he still has to wait.