Male lions in Southern Africa typically live in coalitions.  In the southern African region, south of the Zambezi River, the average coalition size is around two males.  Actual coalition sizes can vary from two males to seven males.
These coalitions are normally made up of lions that are brothers, and often half-brothers, and cousins.  They usually have their beginnings when these males are all still cubs, living in their natal pride.  It has been recorded though that unrelated males may join up and form coalitions later in their lives.

The Western Boys, Mombo, a coalition of two.  Canon 40D, Canon 70-200 f2.8 IS.  1/50s at f2.8, iso 800

These young male lions start showing signs of the bonding behaviour that will ultimately be a critical component of their coalition lifestyle.  They will typically spend more and more time in each others company as they grow older within the pride, and less time with their sisters.  Such behaviour can be witnessed in the way that sub-adult males in a pride will often sleep alongside one another.  They also show their developing independence in the way that start lagging behind the pride when they are on the move.  Sometime between the ages of two and four they may end up leaving the pride.  Their departure may be hastened by the arrival of new adult males, or they may begin to elicit aggression from their own fathers.  They usually leave as a group, made up of brothers, cousins and half-brothers.

Attaining independence can be extremely stressful on the young males, as they have to learn how to hunt for themselves.  They also scavenge whenever the opportunity arises during this period.
They sometimes move big distances during this period, looking for females and food, and either trying to avoid or confront resident male lions.

A coalition of three, the Border Boys, Linyanti, Botswana.  Formerly six, this coalition split into two groups of three each.  Canon 30D, Canon 70-200 f2.8 IS.  1/400s at f/10.  Iso 200

Successful coalitions find females, and gain access to them by chasing away the resident male/s.  These fights can be fatal, and adult males and younger males are often killed in this way.  In several such instances that I witnessed in Botswana where one male of a coalition pair was killed, the remaining male stayed alone and did not accept a new coalition partner.

Once a coalition has gained access to females, they typically become more settled for a while, and spend much time mating and siring cubs.  After a few years, and often when most of the pride females already have cubs, the males tend to become more relaxed in how much together time they spend with each other.  Coalitions may also start to spend more time away from their original pride females after a while.  They leave the females for short periods to patrol their territories, but also to seek other females in neighbouring territories.  Some coalitions can end up holding two or even three different prides of females.  In such instances the males may move between the different groups of females, sharing their time between them.
Another thing that happens is that males within a coalition may also begin to move on their own. Almost invariably these solitary ranging movements by the males are temporary, and are driven by the desire to find new females.  Wandering males typically return, after a day or perhaps a week, to their coalition partners.  This kind of behaviour also places them at great risk, as moving alone often beyond the boundaries of their territories means that they are without the support of their coalition partners should they encounter another male or males.  Wandering males in Botswana would sometimes return to their coalition showing signs of serious fights, and sometimes they don’t come back at all.  In this way a strong coalition can become weakened sooner than one would expect, due to the lack of cohesion amongst the original members.

A male lion in the Savuti concession, one half of a coalition pair.  This male was injured whilst on his own, without the support of his coalition partner, and sustained these scars in a fight with a neighbouring rival male.  Two months later he got killed deep inside another males territory.  Canon 1DMk4, Canon 300f2.8L IS.  1/125s at f/4.0.  Iso 800.

If a coalition is overthrown, and the males driven away, any cubs younger than two years old are at risk of being killed.  When new males encounter females strange to them, they will very often try to kill the cubs.  They do not see the cubs as competition, but rather act instinctively to rid the female of her biological investment in another lions cubs, and create conditions that will lead to females mating with the new pride males as quickly as possible.

Strong coalitions of male lions can lead to stable lion populations as the males are able to hold on to their territories for long enough to ensure the survival of their cubs.

From a photographers point of view, male coalitions open up a range of opportunities.  There is always interaction, usually affectionate, between the coalition members to photograph.  Such bonding moments create a contrast between large and imposing alpha predators and the affectionate side of their nature.  Being able to photograph more than one male lion in a frame also adds much.
Male lion coalitions are an impressive and powerful phenomenon of the natural world, and I try to take photographs that show something of that.