apostrophe - Plural form of "brother-in-law" when a possessive case is involved

1) My brother's friend's opinions

2) My brothers' friend's opinions

I hope "1" and "2" are pretty clear and correct.

Now, let us suppose that the brother in "1" is a brother-in-law and that all the brothers in "2" are brothers-in-law.

Question is: How do we rewrite "1" and "2" in these cases?

Following the J.R.'s suggestion, I have done some preliminary researches and I found that when in-laws become possessive brothers-in-law is written brother-in-law's. So, I would conclude that we should rewrite "1" and "2" in the same way, as follow.

i) My brother-in-law's friend's opinions.

ii) My brother-in-law's friend's opinions.

But, if it is so, how can we distinguish the two different cases?