King Euron Greyjoy is the brother of Balon Greyjoy, the Lord Reaper of Pyke and later King of the Iron Islands, and Aeron Greyjoy, a Drowned Man. He is also the uncle to Balon's children, Rodrik, Maron, Yara, and Theon Greyjoy. After murdering his brother Balon, Euron takes control of the Salt Throne with the support of many Ironborn and seeks to hunt down Yara and Theon, who oppose Euron and have allied with Daenerys Targaryen.
Euron is captain of the longship Silence, the flagship of the Iron Fleet, and wields a two-handed battleaxe in combat.
Euron's personal sigil is the standard Greyjoy heraldry of a kraken on black, but the kraken is silver instead of gold with a third red eye inscribed onto its head.
Euron is named "Commander of the Lannister Fleet" - although he primarily uses the Iron Fleet as his main ships - after he defeats the allies of Daenerys in Blackwater Bay and delivers Ellaria and Tyene Sand, as a gift to Cersei.
(source GOT wiki)