When male lions reach full maturity, usually over the age of two. It is only then that they are ready to take over territory – which means taking over a pride.
The fight between an existing pride leader and the challenger does not always result in death. Most times, if a challenger is successful, the defeated leaves the pride and destined to wander a nomadic life.
When a new male lion takes over a pride, the first thing he does is to kill off the previous males offspring. This is called “Infantcide”. This is where the new king of the pride kills the cubs because they are not biologically related to him, and does not want to spend his energy ensuring that other lions’ genes will be passed on.
However, within days or weeks of losing their cubs, the female lions come into oestrus and mate with the cub-killing male, and produce other cubs.
Why don't you come with me next year. We will experience real life in the Serengeti and we will see cubs of all ages, nomadic males, and entire lion prides living in the Serengeti.
All the details are here https://www.kevinpepperphotography.com/2019-tanzania-photo-safari