I can walk into the exam room and tell who has older siblings.

     I have a lovely picture of one of my families:   a one year old boy is held by his mom with his 12 year old sister on one, side and a 10 year old sister, herself  holding a six year old sister, on the other side.  A little child, or a young person as I like to say, surrounded by love and attention.  It's like having another set of parents, almost, except they're a lot younger and have just learned all this stuff about living not so long ago.
     I've gotten to where I can walk into an exam room and tell that an infant has caring older siblings, or sometimes a father who is very involved with his children.  I can tell because these infants are relaxed, curious, and much less wary of me, compared to others.  I can tell with the older children because they are more articulate and mature and have ideas about their future. 
     There is a wonderful book called Cider with Rosie by Laurie Lee, a story of growing up in rural England in the 1920s, and the opening scene of the book captures the spirit of what I'm talking about.  While moving to a new house, Laurie gets lost in a thicket of tall weeds, and he is rescued by his sisters:

      From this daylight nightmare I was awakened, as from many another, by the appearance of my sisters.   They came scrambling and calling up the steep rough bank, and parting the long grass found me.  Faces of rose, familiar, living; huge shining faces hung up like shields  between me and the sky; faces with grins and white teeth (some broken) to be conjured like genii with a howl, brushing off terror with their broad scoldings  and affection.  They leaned over me -one, two, three- their mouths smeared with red currants and their hands dripping with juice.

Thanks to Penguin Press  1959