I think maturity isn't so much age related. It's an inner quality, like character, that you can't give someone who doesn't have it. Yes, there are some people of 50, 60 and older who have never grown up. They've lived their lives attached to family and their identity revolves around it. Such people don't understand or appreciate those who have lived different lives, and in my experience, they truly cannot see further than their nose. They are cognitively incapable of doing so, and it's far too late now. It's not possible for someone at that age to suddenly 'grow up' and be mature. They've missed out on vital aspects of life, by remaining so attached to their family of origin. Families are fantastic and are the primary social group we know as children. But that's just it. We aren't born to stay forever a child. There's a big world out there and seeing life through a narrow perspective is bound to have a big impact on someone's maturity. In my view, if you can go it alone and do things that might be challenging without constant family around you, and be responsible for your life and whatever decisions you make, that is maturity. Dealing with immature people, whether they throw tantrums or not is a nightmare. Not every immature person throws tantrums, some are totally the opposite and come across as mature, but their attitude and behaviour say otherwise. Some people who throw tantrums may have a tempermental disposition but still be mature. It's not black and white.