In my family it seems like it was oldest to youngest. At least that’s how it looks based on the family pictures. The oldest two (boy and girl) have dozens of pictures of themselves as infants and toddlers. By the time they got to me (#4) I was able to claim a snapshot of me in coveralls playing on a slide for my “baby” picture. I think the last two (#5 & #6) had even fewer pics.
This is true in my family. The family where I’m the mother, I mean. Part of it is the switch from film to digital partway through the sequence, so there aren’t many prints. And I lost a lot in a hard drive crash a while back.
Pictures are a mere reflection of the ‘uniqueness’ effect.
“Don’t waste the film as we already have enough ‘cute baby’ pictures.”