I too have chosen to live far from my family for most of my adult life. In fact, I have only lived within a day's travel of them for about 12 non-consecutive months out of my entire adult life.
There are times when I was in Hawaii or overseas and they were on the US East Coast. I often would only see them every 3-5 years. With the adults there was a little surprise at rediscovering them again and again, but my nieces and nephews were the big surprises.
Each time I would visit, it was as if I was meeting a new set of kids. There was the 3 year old version of Austin, then the 7 year old version, then the 12 year old version, then the 6'3" 15 year old version. Now I see picks of him at 19 and can't believe how he's changed! And that's just their physical appearances. Their personality maintain a certain fundamental identity, but so much about so much changes in how they think and communicate and what their interests are.
I sometimes miss having gotten to spend more time with the different versions of them. I will never see Austin at 3 or Shake at 5 or Dominique at 12 again. Those versions of them are gone forever. And I won't get to have been there to be a part of how they developed on a day to day basis.
Instead I get the life I came to live.
I think this is the hardest part of being away from family. One of my brothers is expecting their first next month yet, when will be the first time we will meet? I haven't seen that brother face to face for 9 years.
You are right, there is a common thread to a person but how it presents depending on what arises can change quite drastically.
This is the thing.