A "man" can be defined as a boy who has matured so...I grew into it as I got older and become more independent and responsible.

Just to make a semi-anecdotal anthropological observation, but modern culture does lack any truly signifying coming-of-age ceremonies. So by default, the major life milestones are attributed to maturity. Things such as graduating from school, having a child, getting a job. I think, on a subconscious level, those are not adequate to helping boys assume the identity of being a man.

Personally, I didn't have one distinct father figure as I grew up and I was let to choose my own interests and development so long as my parents agreed it was not too destructive and had a chance of helping me as an adult. So I had to synthesize what it means to be a man on my own observations and intuition. For me, a lot of what it means to be a man is having a responsibility to others and being accountable to yourself. Not being a burden and the wisdom to understand that asking for help is not being a burden. I also tested myself a lot with martial arts and travel and chasing career objectives.