House Blackberry is a noble house of the Seven Kingdoms. Two members serve House Baratheon of Dragonstone, so the house is probably from the crownlands or the stormlands.
A Storm of Swords
When Ser Davos Seaworth arrives at the gate of Dragonstone after the Battle of the Blackwater, he asks about Jate Blackberry, but the new guardsmen do not know the name and believe him to be dead. Omer Blackberry is one of Edric Storm's protectors when the youth flees Dragonstone.
House Blackberry at the end of the third century
The known Blackberrys during the timespan of the events described in A Song of Ice and Fire are:
Houses of Unknown Regions