[RahulK]

Please consider my explanation in the below image.

First of all, the  parent don't have 4 daughters they have 2 daughters and 2 affected sons ... Yess I agree with you. atleast one of the two daughters should get affected..   I also want the answer to be y linked only.. i just drew the possible outcomes according to answer key..

Sorry for my mistake, they have 2 daughters.

I am just wondering, if my arguments will hold enough to favor my challenge and will it be worth challenging.