“Valaena was half-Targaryen herself, through her mother…”
The Parents of Valaena Velaryon.
House Velaryon arms are depicted as a silver seahorse on a sea green background (field). 
Targaryen Portrait Master list.
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Note 1: The Targaryen and The Velaryon who we have no idea who they are except that they were married and their only known child is Valaena Velaryon. These two could sit on two places of the family tree. The unknown Targaryen could either be a sister to Maegor and Aerys or even an unknown child of Aerys. The Velaryon man is most likely Lord Daemon Velaryons brother. But overall that is completely unknown and all we can do is guess where they place in the family tree.
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Note 2: I decided to go for medieval (early 1300s european wear) for the Velaryon man. I did this because House Velaryon is historically very much apart of Westeros society so they probably integrated into Westeros fashion a lot faster than House Targaryen and House Celtigar did. House Targaryen and House Celtigar are known to be quite isolated from Westeros until after the conquest, hence why I see them wearing old valyria grab for a longer amount of time despite it being out of fashion.
