NARRATOR: The elder sister, the most secretive, returns

with four cubs--

all males.

They're a week or two younger than the twins.

Three are full of confidence, but one holds back.

He might have been called the runt of the litter in the past,

but he's probably just the more tentative character.

[CUBS ROARING]

Each lioness has four teats.

Nevertheless, the new cubs are keen to suckle

with their older cousins.

For the original, confident female twin,

it's an inconvenience.

But for her brother, a lone male, it's salvation.

Four new males-- cousins.

If all survive, they could form a powerful coalition,

and he's the eldest--

potentially the leader.

[LIONESS ROARING]

Lions share suckling duty, called allosuckling.

It forges bonds between litters, and is the foundation

for future prides.