Actually, a group of lions is called a 'pride'. There can be a range of 3 to 30 lions in one pride. If there is a very large animal, a single lion wont attack it, but the whole pride would.
Normally, adult pride males are related, usually brothers, and can number from one to four. The most recorded in one pride was six, in the N'goro Goro Crater in 1989.