This was mentioned in a comment, and I should clear it up: McSI fits into a "modern fantasy setting;" by that, I mean a fantasy setting written recently and with a modern voice. They would be out of place in an Old School setting unless it's very self-aware; they'd be at home in Eberron or Hackmaster but not Shaintar or the Forgotten Realms.
I also forgot to mention that the McSlaughters are both Wild Cards. I will edit their entry accordingly.
That being said:
The McSlaughter Brothers are keen to hire barbarians who are the last remaining members of their tribe, seeking revenge (you'd be surprised at how many of those are running around). They usually work for cheap, fight like demons, and are easily manipulated. Their most recent hire is Grark, the Last Son of the U'hurr Clan. Though dumber than a box of dumb rocks, Grark is the human equivalent of a tac-nuke; the McSlaughters usually try to rile him up about the most dangerous target and send him on his way. Grark is also possessed of a sort of animal magnetism that many women find irresistible, so the McSlaughters occasionally direct him to infiltrate adventuring groups and distract gullible females.
Grark (Wild Card)
Attributes: Agility d8, Smarts d4, Spirit d6, Strength d10, Vigor d10
Skills: Climbing d6, Fighting d12, Intimidation d8, Notice d4, Persuasion d4, Stealth d6, Survival d6, Throwing d8, Tracking d6
Pace: 6; Parry: 8; Toughness: 10(2)
Hindrances: Clueless, Quirk (easily tricked: -1 to resist Tricks), Vengeful (minor)
Edges: Attractive, Berserk, Brawny, Combat Reflexes, Frenzy, Trademark Weapon (Ribspreader)
Gear: "Ribspreader," Magic Greataxe (2d10+1, +1 Fighting, no Parry penalty, AP 2), Chainmail, Metal Pot Helm, 1 healing potion, 1 strength potion (+1 die type for 3 rounds when drunk), 1 blast potion (deals 3d6 damage in MBT when thrown; he is strictly forbidden from using it when the Brothers are in its area of effect), 2 spears