Working subtitle: "I was a dad once".
So, that bit at the end of The Eleventh Hour when little Amelia heard the TARDIS and looked up and then we never found out what happened?
All together now: AAAAAAAWWWWWWWWWWWW.
(Explanation is here
, in fanfic form. But I still want to see them travel together and have awesome adventures that she can't tell him about when she meets him again twelve years later. XD)
*edit* ZOMG THAT ONE SCENE IN "THE BIG BANG"!