May I stick my oar in?
To me, this is a photo of a young-ish couple with their mother/mother-in-law & 3 children - 2 girls & a baby.
Or perhaps a young-ish couple with their first baby, with mother/mother-in-law & HER daughters.
The 2 girls are in mop-caps; the eldest looks much younger than 17.
The baby's parents, particularly the mother in adult dress (with hat), could be in their 30's ...
The trouble with photos is that we see what we want to see - this could be a friend sending a picture of THEIR family ...
Sorry BH
Jane