Puzzle on the minimum number of distinct people

Question

There are 12 photos and there are 3 women in each of the 12 photos, left, middle and right. In each photo, the woman in the middle is the mother of the one on the right, and the woman in the middle and the woman on the left are sisters. If I tell you the 12 women in the middle of the 12 photos are 12 distinctive women, what’s the minimum number of distinctive women that can satisfy the criteria above?

The answer is clearly between 12 and 36. But what’s the minimum number possible?

Note: not a riddle. No step-sisters, no divorces or weird marriages, no conjoined twins, or any other tricks. Pure mathematics puzzle.

Answer 1

One of promising configurations: $19$ woman:

      A             B
    /   \         /   \
   C     D       E     F 
   |    / \     / \   / \   
   G   H   I   J   K L   M
       |   |   |   | |   |
       N   O   P   Q R   S

where A and B are sisters; C and D are sisters; E and F are sisters etc.

And photos: BAC, ABE, DCG, CDH, FEJ, EFL, IHN, HIO, KJP, JKQ, MLR, LMS.