Aki of Clan Brokvar was the younger brother of Udalryk. According to the most widespread version of events, that which is told to Geralt by Cerys, Aki died out at sea while on a trip with Udalryk. He fell overboard when a storm broke out, and Udalryk was unable to save him because he was busy tending to the sails and did not hear his brother until too late.
Aki's father bestowed him with Brokvar, an ancestral sword of the clan. This act was against the general custom which dictates that the sword should have passed to Udalryk, the eldest son. It is because of this that some folk on the isle doubt the validity of the account of Aki's death, believing that, perhaps, Udalryk may have deliberately allowed Aki to die as he harboured hostile feelings towards his younger brother over the sword.
Later in his life, Udalryk named his newborn son Aki, in honour of his late brother. Aki's bones can now be found laying underneath the sea by Ulula's Needle at the mouth of the bay of Spikeroog while presumably his skull is in the chest on the island as well.