Sister Sizing is an alternate bra size. Simular but not the same. 32c ,34b , 36a are Sister sizes.

Explained: What is Bra Sister Size with Sister Size Charts

32B Bras: Understanding the Cup Size, Equivalents and the Perfect

What Are Sister Bra Sizes?

What is my bra size?

They Don't Have Your Bra Size? Try Your Sister Size for a Great Fit

Simply Perfect By Warner's Women's Underarm Smoothing Wire-free

Is 36C the same as 34D in bra size? - Quora

What Are Bra Sister Sizes And Why Do They Matter? - SHEFIT

What Are Sister Bra Sizes?

Understanding Sister Sizing to Find the Perfect Sports Bra Fit