Questions from yesteryears

This photograph accompanied my father during the war years when he served in places as far a flung as Egypt and Burma. It is a portrait of brothers John, baby Jimmy and sister Christine Rhona.
Included in items unearthed at brother Jock’s (John) during a recent tidy are a receipt for the pram that was purchased following the birth of Rhona and three locks of hair taken when sister and brothers were born.
These mementoes raise a number of questions:
1. Did the pram (cost £4:7.6 equivalent to £296.61 today) service all three?
2. Which lock of hair belongs to who? and
3. Why remove and keep a lock of hair from a new born?
Science and genetic testing could provide the answer to 2 and folklore the answer to 3 but the answer to 1 will remain conjecture as all who could answer have past.