Family inherent magic as it applies to individuals

[Suzanna Stormborn]

I don't think we'll ever get a clear-cut answer.

Going back to my earlier comment, Bilbo found the Ring, because it wanted to be found, and had been stirred up when Sauron returned to bodily form. But, over and above that, God wanted Bilbo to find it.

There will be several possible reasons why Dany was the one to hatch Dragons. She might be AA reborn; R'hllor may have chosen her to bring magic back into the world; magic may be an unknowable force, which was due to return to the world, and used her as it's catalyst; the spirits of her ancestors may have chosen her to hatch the eggs. Or maybe, she just got lucky.

I agree, but my point is that Dany is not the only Targaryen who is special in her family. Any Targ who was able to bond with a dragon is, and any of them who had the higher-heat tolerance. Dany is one of them, Aegon V is one, All the dragonriders from PATQ are. She is not the only one, she may be AA or TPTWP, but that is not what I am talking about. She bonded with an unborn dragon, heard the dragonsong, knew inherently what to do with the eggs. NO one else we have seen has done anything like that. Viserys didnt know what to do with the eggs, he wanted to sell them (a thought which never crossed Dany's mind). I think it is blaringly obvious that Viserys had no connection with the eggs, had no intentions of hatching them and has nothing special about him at all. Which is a perfect example of 2 members of the same 'magical' family, and 1 has the gift, and the other doesn't.

[Fool of a Book]

I've always suspected that GRRM has the Targs historically marry sister/brother precisely because the "blood of the dragon" needs to be rare for plot purposes, bastards and Blackfyres aside (since none are confirmed in the current events of the story).

Just like First Men are mostly muggles with a few wargs, Targs have their squibs like Viserys and the unsuccessful dragonseeds.