Answer: This problem may arise when your father never bought a shoe before. A male is bad at buying accesories and guessing the size, so the mother should have bought a pair of shoes. Or it can also be that your father has a short term memory or that he never knew the size of your feets. The feet might also have irregular growth for which it grows more than the normal size but such cases are rare to be seen.
You can prevent this by going with your father and selecting the shoe of your size. Or you can simply send your mother to buy it for you instead. Or another perfect choice could be is that you just dont ever send your father to buy anything for you or just never buy a pair of shoes. Wear the shoes that you always did or buy it yourself since your the one who is supposed to know the size of your feets. Another possible solution could be that you can make use of the money by gifitng them to someone close to you.