Those pigs are Spartan Strategoi

[Kyros]

In case you were looking for images, as I didn't find anything here or on Reddit.

https://steamcommunity.com/sharedfiles/filedetails/?id=1537715997
https://steamcommunity.com/sharedfiles/filedetails/?id=1537715964

It seems they tend to appear more often in fortified controled regions (T3), you can find them in big cities, sometimes in forts, and wandering the land on a horse. You get at least 1 guaranteed kill if the battle for control is available. Not in the battle itself afaik but in the Spartan war camp.

Felt really bad killing brothers. But first I guess