Half-Generations

I have a younger half-brother, a child of my father's second marriage. I did not meet him until I was 18 and he was 4, and he was a child to me rather than a peer for many years.  In fact he was the same age as our various foster children, so my father and I both had eight-year-old boys at the same time, and our last foster daughter had a crush on him when they were seventeen.  He is now a peer, and I no longer think of him as a half-brother, but simply my brother. This was gradual, but a long time ago. 

He was 12-16 years older than our first two children, whom he saw as children at first. But he and my second son work in similar industries and speak together as peers now.  I think it has been comfortable for him to speak about difficult issues with me because I am not his parent, but also don't need to be given a lot of background on any story.  I think it has also been easy for my sons to become peers of his for the same reason.  He is not their parent, yet there is no need to give a lot of context for situations.

My wife visited her college roommate over the weekend, who was an only child but the youngest of a group of cousins.  In this way she was also close to both the mothers and the daughters growing up, and as both of her parents died when she was in her 20s, she has made the effort to keep up with them.  

I don't know if these half-generation situations are more common now or less common than they were.  Families had more children spread over more ages, but there are also more blended families now.  But I think there is significant advantage to having a person like this in your life.