I've actually heard about some study that girls are attracted more to older men if they have a dad that was fairly old when they were born, like about early 40s or older.
I don't know, just about any Grayza hint or Erza X Anyone but Jellal/Gerard hint is overshadowed by the somewhat canon Jerza/Gerza. But I'm sure there's a couple of good Grayza hints in the series. After all, I've only got into Fairy Tail recently.