Siblings - Almost

A 5-yr-old, in one of her first lessons, had her fingers all squished up on her bow.  In an effort to give them a bit of breathing room, I asked:

Me: Do you have any brothers or sisters?
Girl [with a look of 'surely you know this']: Well... yes... but they're still in mummy's tummy.

I should point out that her mother was about 8 months pregnant with twin boys at the time.