I was reading in Eat, Pray, Love that babies in Indonesia are often (if not usually) named in order, literally
One (for the first child)
Two (for the second child)
Three (for the third child)
and so on. So each child always remembers what their birth order is because it's their name. Eka means firstborn and is given to the first child (male or female). Dwi means secondborn and is given to the second child.
Is this really true? Wouldn't that be confusing in school if you had a classroom full of lots of Ekas, Dwis and so on? It would almost be great to be the fourth child because hopefully there would be fewer people with your name (although I don't know what the average fertility rate for an Indonesian woman is).
OK you know I had to look it up
Apparently right now it's about 2.2 in 2008 - so if you are the third or fourth child, you are lucky because fewer people will have your name!