In Tagalog vernacular, ubusan ng lahi can be roughly translated as "extermination of the family line" - specifically, extermination of the family and close relatives of your opponent until there is no one left who cares enough to avenge their deaths.
Although some people consider ubusan ng lahi a descendant of the Islamic "blood feud", there are significant differences from the Islamic concept of blood feud, as ubusan ng lahi is not sanctioned by any church, government or higher power - it's strictly a vigilante action. It most probably can be traced to ancient tribal disputes, although while the ancient Malay and other indigenous tribes practiced "an eye for an eye", ubusan ng lahi is more along the lines of "do unto others before they can do unto you".
This is common in rural areas in the Philippines (especially in Visayas and Mindanao) where political families battle for control of mayorships and governorships. Recent incidents include the Espinosa killings in Masbate (the latest was in May 2001) and several murders in Nueva Ecija (in which a couple of my relatives got caught in the crossfire). Some families (especially Muslim clans in Mindanao) have been at it for centuries.
A popular script for local action films goes somewhat like this:
Hero watches villain's goons hunt down his family one by one. In some movies, the hero is a baby, in others, he's a helpless child. The villain then takes the family's money/land/both for himself.
The hero is squirreled away to live in poverty with an old man (or old couple) and his past is kept hidden from him. Typically, he's the heir to vast fortunes, or at least heir to a political career.
Hero learns about who killed his family, and swears revenge. Then comes the obligatory training sequence, where the old man reveals his true nature as a sharpshooter/ninja/kung-fu master, and proceeds to teach the young one everything he knows. This usually comes with the standard shooting-the-tin-cans-off-the-rock practice scene.
The villain, who by now has parlayed his ill-gotten riches into a successful political career, gets wind of one last survivor who could jeopardize his new-found respectability, and proceeds to send his goons out to take care of the hero. They fail, but they do manage to fatally wound the hero's teacher, who then makes the hero promise to avenge him in a drawn-out death scene.
The villain then kidnaps the hero's love interest, holding her as bait to draw the hero into a trap.
Then comes the big fight scene, where our hero charges into the trap, kills every single one of the villain's goons and immediate family (who, inexplicably, are all toting guns and hanging around the main villain), saves the girl, and gets his honor back (as well as his family's land titles, Swiss bank accounts, and political party affiliations).
I believe this is also a fairly common recurring theme in
Japanese folklore and cinema (i.e.
clannicide).
Come to think of it, there's something vaguely
Luke Skywalker-
Obi Wan Kenobi about this whole business, although Lucas may have been influenced by Japanese or other Asian films.