@AnnaMagnani
We experienced all of these from FIL who appeared to have formed images of all his children aged about 8 and despite them now being 40, he still had them down as 'the responsible one' 'the reckless one' and so on. Fine if you were the responsible one but poor BIL apparently couldn't be trusted with money based on his breaking a window with a football as a child. 
Hmm, funny one that. I experienced this kind of shit too. I am the youngest of 7 cousins, (all born in the 1960s.) I am the youngest, but there's only 8 years between me and the oldest one. I was the quietest, and quite shy and studious as a child.
The second and third youngest are only just over a year older than me, yet I was the only one treated like a bit of a daft child by several extended family members. Even when I was in my 20s and 30s.
Much mockery and LOL-ing ensued when I got a passport and said I was going backpacking around Europe with a friend when I was 19. 'YOU! You will be dead within a day' roared an uncle. 'You won't even make it to the ferry across you won't, you couldn't tie your shoelaces til you were 8!' hooted an auntie.
Then there was the 'oooh she's got a BOYfriend!' type comments
And 'have you done it yet?' from my cousins, when I was 17/18
And the chuckling and mocking when I started taking driving lessons. 'Keep out of the fields everyone, and off the footpaths, Robin's attempting to drive' a couple of uncles said!
I had the last laugh though when I was the first of the 7 cousins to pass my test AND get my own car. They shut up then.
I also got some raised eyebrows when I announced I was getting married (at 27!) Like 'what you?' In their eyes and their minds, I was still the shy and bumbling little girl who couldn't tie her shoelaces til she was 8, and spent all her time reading, writing stories, and drawing.
And the same 'what YOU' comments came when I was pregnant with my first child too. Married, nearly 30, own home, and a successful career, and they were like 'YOU with a baby?!' 
I even had one incident when I was 33, and on my lunchbreak at work, and a van driver nearly hit me when I was walking across a zebra crossing. I shouted 'TWAT!' as he flew past. Unbeknownst to me, my cousin (2 years older than me,) was 100 or so feet behind me in a shop doorway. She went straight to my mother who lived 15 minutes walk from her, and told her! My mother left a nasty, condescending message on my answerphone at home saying I should be 'ashamed of myself for my behaviour.' 
No surprise then, that when my parents died (six months apart - 10 years ago,) I left the area, and never looked back. I've had nothing to do with anyone of them since.
Only my brother who moved to Canada in 2007. I still have him in my life, and his wife and 3 kids, though I don't see him often. (HE has nothing to do with the extended family either. He also stopped the contact when our parents died..) And I also have contact with 2 great aunts on my dad's side (and their 2 daughters, my second cousins, who have one child each,) who live 50 miles away and moved in the 1990s. CBA with any of the others... I ghosted them, as they brought NOTHING to my life.
As you say, some family members still see certain younger people in the family as that child who was clumsy/nerdy/a bit behind his or her peers/shy etc, as the child they were. They can't seem to get their head round the fact they are a totally different person now. A responsible, intelligent ADULT who is probably more capable of doing most things than them!