Who buys the children presents for mothers/fathers day, birthdays and Christmas?

With mothers day being Sunday just curious to what everyone thinks. I have a step-daughter (8yo) and a daughter (11months) Both parents of my step-daughter is in a relationships, her dad is with me and her mum is with someone. Do you think it should be the other parent? (So in this case the dad) Or the partner? Personally we have bought for her mum every year but this year we haven't because her partner always gets her stuff.