Yes, this is a headcanon post for Papa and Mama Baratheon that also manages to compile the bits of canon we have on them, as GRRM gave us so very, very little canon as of yet (I have hopes this might change though.) I have to use my powers of deduction and screenwriting (film student here, babies) to create a backstory of sorts for both of them.



What we have from canon:

• Steffon is the son of Rhaelle Targaryen and a yet-to-be named Baratheon Lord.
• Cassana is the daughter of a yet-to-be named Estermont Lord and the sister of Eldon and Lomas Estermont.
• Steffon and Cassana are the parents of Robert, Stannis and Renly Baratheon.
• This makes them the grandparents of Robert's obscene amount of baseborn children and of Shireen Baratheon.
• And also the parents-in-law of Cersei Lannister, Selyse Florent and Margaery Tyrell
• As Steffon is also a Targaryen, they are also the uncle and aunt of Rhaegar, Viserys and Daenerys Targaryen, the cousins of Aerys and Rhaella Targaryen and the grand uncle and aunt of the children of Rhaegar and Elia Martell.
• Oh, and also the uncle and aunt of Andrew Estermont.
• Going back to the Targaryen family thing, Aerys sends them to find a bride for Rhaegar in the Free Cities. They fail like pros in the matter but they find Patchface.
• And, in a typical "Rocks fall, everyone dies" moment  of those that GRRM seems to love much, when they where about to reach the coast of Storm's End, there's a storm (how fucking appropriate, by the way) and their ship crashes rather messily against the many rocks of the coast. As we know, the only survivor is a Patchface that well, left his mental sanity in the sea too.

Verging into headcanon territory (aka, could be far easier supported by canon than other things here in this list unless GRRM decides otherwise)

What we can gather from "A Clash of Kings"

Patchface had come to them as a boy. Lord Steffon of cherished memory had found him in Volantis, across the narrow sea. The king- the old king, Aerys II Targaryen, who had not been quite so mad in those days, had sent his lordship to send a bride for Prince Rhaegar, who had no sisters to wed. "We found the most splendid fool" he wrote Cressen, a fortnight he was to return from his fruitless mission "Only a boy, yet nimble as a monkey and witty as a dozen courtiers. He juggles and riddles and does magic, and he can sing prettily in four tongues. We have bought him freedom and hope to bring him home with us. Robert will be delighted with him, and perhaps in time he will even teach Stannis how to laugh." It saddened Cressen to remember that letter. No one had ever thought Stannis how to laugh, least of all the boy Patchface. The storm came suddenly, howling, and Shipbreaker Bay proved the truth of its name. The lord's two- masted galley Windproud broke within sight of his castle. From its parapets his two eldest sons had watched as their father's ship was smashed against the rocks and swallowed by the waters. A hundred oarsmen and sailors went down with Lord Steffon Baratheon and his lady wife, and for days thereafter every tide left a fresh crop of swollen corpses in the strand below Storm's End.
Prologue, narrated by Maester Cressen

Stannis stood abruptly "R'hllor. Why is that so hard? They will not love me, you say? When have they ever loved me? How can I lose something I never owned?" He moved to the south window to gaze out at the moonlit sea. "I stopped believing in gods the day I saw the Windproud break up across the bay. Any gods so monstruous as to drown my mother and father would never have my worship, I vowed. In King's Landing, the High Septon would prattle at me of how all justice and goodness flowed from the Seven, but all I ever saw of either was made of men."
Chapter 10, Narrated by Davos

Stannis pointed his shining sword at his brother. "I am not without mercy," thundered he was notoriously without mercy. "Nor do I wish to sully Lightbringer with a brother's blood. For the sake of the mother who bore us both, I will give you this night to rethink your folly, Renly. Strike your banners and come to me before dawn, and I will grant you Storm's End and your old seat on the council and even name you my heir until a son is born to me. Otherwise I shall destroy you."
Chapter 31, Narrated by Catelyn

• These excerpts actually tell us quite a bit about both Steffon and Cassana through her children and even a bit (in the case of Steffon) through himself.
• In the case of Steffon his way of writing feels quite similar to Robert's way of talking, without sounding as coarse as his son.
• So, Steffon's personality and way of being would certainly be very similar to that of Robert Pre- Rebellion and marriage to Cersei.
• And while Robert (and Renly too, to a certain extent) takes a lot from the paternal side of the family, I can certainly see Stannis taking more from the maternal side.
• He certainly gives more importance to his mother than to his father from the quotes I managed to find, mentioning her first in the first quote and sort of invoking her as a way of a pacifying spirit before threatening his brother. So, irony of the situation aside, that leads me to believe that in life she actually was the one who would bring peace between Stannis and Robert should there be a quarrel between the two, when they were kiddos.
• And, as Robert most surely reminded Steffon of himself and probably his father too, the elder Baratheon was his father's favorite. Even though the Stannis mention in his letter makes me think he also harbored a lot of love for his second son, just not to the extent he had for Robert.
• The "A wiki of Ice and Fire" page on House Estermont describes Lord Eldon as an "old -fashioned, cautious man". Though this doesn't exactly apply to current!Stannis, I can see Cassana seeing more similarities in young!Stannis with her papa and her siblings than with the Baratheon side of the family, and perhaps doting a wee bit more on him than on Robert.
• Renly was just a babe at the moment of Steffon and Cassana's death so I cannot really elaborate as much as I did with his brothers. But as he was healthy and he was a boy, it's pretty sure that he was really loved and welcomed by his parents.
• Going back to Cassana, I don't exactly see her as being absolutely old-fashioned, but certainly a motherly type that would make her children and taking care of the household her life. But also a intelligent woman, as Steffon would apparently take her counsel on several matters, such as the help for finding their nephew Rhaegar a bride.
• So I very much see them as a loving couple (I will elaborate on this on the "Fanon, verily" section) who doted on their children and tried to be the best rulers possible for the Stormlands, something that would have made them terribly missed by all after their deaths.

On Steffon and Cassana's ages and birth years

• The Date of Birth of Eldon Estermont, Cassana's eldest brother, is dated by awoiaf as "+/- 230 A.L."
• If we take it as a fact that would make him 48 in the year 278 A.L. (The year of Steffon and Cassana's deaths) and 68 in 298 A.L. ( the year in which the first novel "Game of Thrones" takes place.)
• Unless the current Lady Estermont at the time (aka Cassana's mother) was a mega-fertile woman of the likes of Elisabeth de Hesse Darmstadt or Isabella D' Angouleme, it might have taken a bit of time from pregnancy to pregnancy, or at least pregnancies that resulted in birth, because there's always the not so uncommon (go and ask Lysa Arryn) opportunity of miscarriages.
• Robert's birth date is stated to be 263 A.L. , making him 15 when Steffon and Cassana die.
• Stannis's birth date is stated to be 265 A.L., two years later, making him 13 at the moment of his parents' death
• And finally Renly's birth date is 278 A.L., making him just a few months old.
• Because this IS SPARTA is a medieval fantasy setting, one can imagine that Steffon and Cassana got married young and probably started working on the making a heir department pretty soon. (I have a theory but that goes into the "Fanon, verily" department)
• Thus, at least Cassana should have been 14-15 when she married. Probably 14 when she was bethroted and 15 when she was married.
• Steffon's age poses a wee bit more of a problem since it's not something that can be really measured thanks to his children's ages but something tells me that he is in age, something between Cassana and his cousin Aerys. So maybe 16-17 at the time of his bethrotal-marriage.

•  So, that would make him 32 and her 30 at moment of their deaths.
• In conclusion, I would place Steffon's birth year at  246 A.L. and Cassana's birth year at 248 A.L.

(To be continued as soon as possible)