User blog:H-Man Havoc/Who is older, Jon or Dany?

Since both sides of Jon's parentage are known (maternally confirmed, paternally obvious but not officially stated in the series yet aside from the leaked HBO diagram), I'm curious to find out if either Jon or Dany are older than the other, and if so then by roughly how much. Both of their ages are given as 21 by the end of season 6 (as per their infoboxes and related reference tags), and we know that they were born at the tail-end of Robert's Rebellion, if not in the aftermath.

While aunts/uncles being younger than their nephews/nieces is a rare situation, it does occur and it isn't uncommon for a pairing to be just a few years apart (e.g. retired MLB stars Dwight Gooden and Gary Sheffield are uncle/nephew, respectively; both are roughly 4 years apart in age).

If I had to guess, I'd say they are at most two months apart (Dany being the older one) and at least (which would be ironic given the tragedies accompanying their births) born on the same day.

Both are also very likely The Prince That Was Promised, as the term "Prince" in High Valyrian is meant to be gender-neutral. Was there anything in the books that could strengthen the argument that both claimants would ideally be of similar, if not exact age?

What do you guys think about this? Should the two meet next season or season 8, would we likely find out once and for all?