It´s correct and not so unheard of, in this case we are talking about two references, one is Gordon´s brother (the Brother of Gordon), next we are talking about the (Brother´s killer) the "killer of the brother".

Taken backwards (similarly to our saying that in English to Portuguese we read backwards) then it would mean "The killer of the brother of Gordon."

Reverse the sentence,  put apostrophes in-between and voilá! Here we have the initial sentence standard.

It takes some time and training to get used to it (the structure), though.