2x 1x Felag (We rip apart the other Felag and Horra won't have a numbers advantage anymore!)
Sadly, this is inccorrect. He has somewhere north of a Felag's worth of people at home (it's like 12 families...add in Horra's kids and any of their kids who are old enough and we're talking around 20 people)
and one remaining bandit gang of about 7. I'd say in total he still has about 2 Felags worth. He just had 3 to start with.
Our own assets have also grown to the tune of two very large men with a propensity for violence. So that's handy. We're actually getting to full felag size for the final confrontation (we now have us, Abjorn, Stigmar, Gabriel, the twins, Aki, Stigr, Halfdan and his two sons, Steinarr, Abjorn's dad, and plausibly a few others like Aki's dad, Stigr's other brother, Eric, or even Abjorn's brother).
But really, outside his kids (and plausibly even including some of them, like his daughter), a lot of the above assets may desert Horra if we get him outlawed. He's not the sort of guy who inspires 'go down with the ship' kind of loyalty.
We do know there's another unnamed Horrason as well, the one who was with Hod at the ice battle.
1x ??? Osborn Burrison ??? (Married) - By process of elimination this is the only brother 'left' among the 3 of Lori Burisson, Osborn Burisson, and Hod Horasson in the Ice Battle.
The Burrisons aren't really part of this, I don't think. We have no evidence they are, anyway. The one we killed was a Burrison, but we paid weregild so it's over unless we poke them. Certainly there's no evidence of an alliance between them and Horra per se.