It is not difficult to tell which grizzly bear is dominant in this situation. Alone and vulnerable, siblings will often stay together for some time after their mother abandons them, eating and sleeping side-by-side, and even denning together. The average breeding age for female grizzlies is 4.5 years. Males reach sexual maturity at roughly the same age as their female counterparts. So if they stay with their mother for two years this means they may spent two or three years together until a female becomes pregnant or if two males longer.