Who is maternal grandfather of Aegon VI?

[Prince Yourwetdream Aeryn]

I hope he is not Estermont too.

[Bael's Bastard]

Prince Maegor Targaryen 

But seriously, we don't know the name of Elia's mother, or the identity of her father.

[Jaehaerys Tyrell]

The strongest candidate would be a Gargalen, as Doran was fostered there as a boy and we see many nobles serving as pages and cupbearers at the castles of their mother’s families. We also see a whole bunch of nobles serving at the castles of non-relatives though so really we have nothing to go on until GRRM tells us. 

[Bael's Bastard]

6 minutes ago, Jaehaerys Tyrell said:

The strongest candidate would be a Gargalen, as Doran was fostered there as a boy and we see many nobles serving as pages and cupbearers at the castles of their mother’s families. We also see a whole bunch of nobles serving at the castles of non-relatives though so really we have nothing to go on until GRRM tells us. 

Interesting, I hadn't caught the fact that Doran had squired with House Gargalen. Lord Tremond Gargalen is also among those that doesn't drink to the toast for Tommen in ADWD.

[Aline de Gavrillac]

Doran's father.  A Martell.  The previous Prince of Dorne.

[Prince Yourwetdream Aeryn]

2 minutes ago, Aline de Gavrillac said:

Doran's father.  A Martell.  The previous Prince of Dorne.

He was not Martell. He was Prince Consort of Dorne.

[Ser Leftwich]

Some man, no doubt. Most of them are.