The Second Sons are a mercenary company found in the Free Cities. At Yunkai, where they were contracted to face Daenerys Targaryen and her forces, they numbered five hundred men. Their banner is a broken sword.
Their camp is a circle of ragged tents. There is a cook tent. Brown Ben Plumm’s tent has painted canvas walls cracked and faded by years of sun and rain, within the tent are camp stools and a tresel table, a rack of spears and halberds and a floor covered with threadbare carpets in half a dozen clashing colors.
The Second Sons are amongst the oldest of the free companies. They do not enjoy the shining reputation of the Golden Company, but they have won some famous victories. 400 years ago the Second Sons stood in defens of Qohor a long with the Bright Banners company, Against the first Dothraki Khalasar to venture east since the fall of Valyria. However they suffered a defeat and fled the battle field, though the battle was later won by the Three Thousand of Qohor.
Under the command of Mero, whose evil reputation is known even in Westeros, they turned near as bad as the Brave Companions. Mero’s reputation has fallen to the point where none of the Free Cities will hire him any longer.  That is why the Second Sons are in Yunkai when Daenerys marches on the city. They have fought in the Disputed Lands.
The names of every man to serve with them is written in a book, when they joined, where they fought, how long they served, the manner of their deaths. The Second Sons are on their fourth book. The book is leather bound with iron hinges, and large enough to eat your supper off. Inside the heavy wooden boards are names and dates going back more than a century.
A tradition of the company is to sign in red ink. There was a time when each new man wrote his name in his own blood, but that tradition faded as blood makes poor ink.
There are famous names in the books, some from the Seven Kingdoms. Aegor Rivers served a year with them, before he left to found the Golden Company. The Bright Prince, Aerion Targaryen and Rodrik Stark, the Wandering Wolf also served. At present, with the addition of Tyrion and Jorah Mormont, they number five hundred and fourteen members.
Tyrion Lannister's debts to the Second Sons
Part of Tyrion’s negotiations with Brown Ben Plumm for becoming a Second Son included becoming indebted to them. Just prior to signing the Second Sons book Tyrion is handed a pile of roughly fifty to sixty promissory notes to sign. Tyrion remarks that only one in ten Second Son receives a promissory note.
Tybero "Inkpots" Istarion hands him a quill, and ink from Old Volantis - which he tells Tyrion will last as long as maesters' black. Tyrion signs each note Tyrion of House Lannister and passes them one at a time to Inkpots, who dusts each one with fine sand.
The promissory notes:
- To the serjeants: parchments promising to pay the bearer of the note 100 golden dragons
Below the serjeants’ notes the amounts suddenly grow larger, Tyrion is starting to pay the bearer 1,000 gold dragons. The last three notes are made out by name:
- To Kasporio the Cunning: written in fine vellum, promising 10,000 dragons
- To Tybero Istarion: written in fine vellum, promising 10,000 dragons
- To Brown Ben Plumm: inscribed upon a sheepskin scroll, promising 100,000 golden dragons, 50 hides of fertile land, a castle, and a lordship.
After he is done signing the promissory notes Brown Benn tells Tyrion that it is time to make him one o’ them and gets Inkpots to fetch the Second Sons book. Inkpots brings the book and unstops a pot of red ink, however Tyrion elects to sign in the traditional way - with blood. He explains to Inkpots that Lannisters love tradition and to lend him his knife.
He pricks the ball of his thumb and squeezes out a fat drop of blood into the inkpot, trades the dagger for a quill, and scrawls Tyrion of House Lannister, Lord of Casterly Rock, in a big bold hand, just below Ser Jorah Mormont's more modest signature. Inkpots then turns the book around and dusts the page with a bit of fine sand. 
The Second Sons armorer is Hammer; his apprentice is Nail. The Second Sons keep their company armour in six big wayns drawn up near the center of their camp. Under roofs of bent wood and stiffened leather, the wagon beds are heaped high with old weaponry and armour. Most of the iron is not very good; it is not just old and ill-fitting but dented, cracked and brittle with dried blood or rust. According to Ser Jorah Mormont there is some sound steel in there, none of it is pretty, but it will stop a sword.. Some of the armor in the wayns are what sellswords were wearing when they died and some of it is made to fit boys.
Ser Jorah Mormont clads himself from head to heel in company steel. His greaves are mismatched, his gorget is spotted with rust, his vambraces rich and ornate, inlaid with niello flowers. On his right hand is a gauntlet of lobstered steel, on his left a fingerless mitt of rusted mail. The nipples on his muscled breastplate have a pair of iron rings through them. His greathelm sports a ram’s horns, one of which is broken.
Upon entering one of the wayns Tyrion and Penny find a rusted iron half-helm and then a greathelm, a crossbow, a morningstar, a warhammer, a studded mace, and half a dozen longswords. Tyrion finds a dirk he likes - a nasty piece of steel with a triangular blade with a bit of rust on it. He finds a wood and leather sheath that fits and slips the dirk inside. He remarks that the longsword Penny picks up is notched, denoting that it is cheap steel. He examines a heavy shirt of iron mail so full of holes it almost looks moth eaten. The Second Sons' company steel is worse than what he fought in at the Battle of the Green Fork.
- Mero, better known as the Titan's Bastard
- Brown Ben Plumm, captain and commander
- Kasporio, the Cunning, second in command
- Tybero Istarion, better known as Inkpots, paymaster
- Hammer, blacksmith and armorer
- Nail, apprentice to Hammer
- Snatch, serjeant
- Uhlan, serjeant
- Kem, young sellsword
- Bokkoko, axeman
- Ser Jorah Mormont, sellsword
- Tyrion Lannister, assistant to Inkpots, (Penny: attached to Tyrion, she does not sign the Second Sons book)
A Storm of Swords
The Second Sons were employed by Yunkai to defend them against the threat of Daenerys Targaryen. They were placed on the left of the defensive line that faced Daenerys's army. they were commanded by Mero, known as the Titan's Bastard. Mero attended the parley with Daenerys and decided to mull her offer of switching sides or departing only on the condition that she give him a wagon of wine. He brought the wine back to his men and while they were getting drunk on it that night, Daenerys sent her forces on the attack. The Second Sons were routed and Mero fled before he could be captured.
A Dance with Dragons
Daenerys sent them south to guard Meereen against any incursions by Yunkai. However when Brown Ben Plumm learns that Daenerys cannot control her dragons anymore and use them against the Yunkai, he has his company go over to the Yunkai.
References and Notes
- A Storm of Swords, Chapter 42, Daenerys
- A Storm of Swords, Chapter 8, Daenerys I.
- A Storm of Swords, Chapter 42, Daenerys IV.
- A Dance with Dragons, Chapter 66, Tyrion XII.
- A Storm of Swords, Chapter 42, Daenerys
- A Storm of Swords, Chapter 57, Daenerys
- A Dance with Dragons, Chapter 2, Daenerys I.
- A Dance with Dragons, Chapter 36, Daenerys VI.
- A Dance with Dragons, Chapter 50, Daenerys VIII.