Cassana Baratheon

"For the sake of the mother who bore us, I will give you this one night to reconsider."

- Stannis Baratheon to Renly Baratheon

Cassana Baratheon née Estermont is an unseen character in Game of Thrones. She is deceased when the events of the series begin and is not expected to appear in the series. She is the mother of King Robert Baratheon.

Background
Cassana was born to House Estermont, a noble house from the Stormlands. She became the Lady of Storm's End and the wife of Lord Steffon Baratheon, the head of House Baratheon, one of the Great Houses of Westeros. They had three sons, Robert, Stannis and Renly Baratheon. She lived with her family in Storm's End.

Season 1
She has an entry in the The Lineage and Histories of the Great Houses of the Seven Kingdoms, as read by Eddard Stark.

In the books
In the A Song of Ice and Fire novels, Cassana comes from House Estermont. She married Steffon Baratheon and bore him three sons as in the series. She accompanied him on a trip to Essos. Their ship, the Windproud, sank in Shipbreaker Bay within sight of Storm's End on their return voyage. Their bodies were never found.