Squib or muggle - who's a late bloomer?

[lizvega2]

No: HPFGUIDX 89187

I was rereading some random JK interviews, and in one quote she said 
that someone very late in life (No specific age given), who has 
never shown any ability for magic previously, will be able to do 
magic in very desperate conditions. 

I'm sure it's been discussed, but anyone have a thought on who this 
could be?

Obviously a few names come to mind: Petunia, Dudley, Filch or Mrs 
Figg. Or, perhaps someone else not mentioned above, or still 
unknown? Although, it's getting late enough in the series, it 
wouldn't be as meaningful if we weren't invested in this character. 

Petunia would be great, as she's already shown an understanding of 
the wizarding world, and on some level, showed concern for Harry 
when she got Dumbledore's howler. And, I still think there's 
something else problematic regarding the charm Dumbledore placed in 
the Dursley's home. The word 'pact' was used, which would indicate 
that perhaps, Petunia, received something in return for taking Harry 
in the first place? 

I think Dudley being able to do magic would be hilarious. He'd 
probably give himself a tail!

Filch would be terrible, he'd just find ways to seek revenge on the 
students if he could finally hex them.