Question 10300
Try 31 donuts

 Gives away half of them and 1/2 donut to mom This is 16 donuts gone
leaving 15 donuts. Gives half of remainder and 1/2 donut to aunt. This is 8 donuts gone leaving 7 donuts. Gives half of this and 1/2 donut to sister.
This is 4 donuts gone leaving 3 donuts which is 1/4 of a dozen.

I used an equation and perhaps I can redo this solution later and show how I got the equation.