The First Circuit affirmed the agency's decision. "[T]he record adequately supports the IJ's finding –– which the BIA accepted –– that the threats against Marín stemmed not from Marín's kinship ties per se, but rather from what Marín did and Cuellar's desire in response either to seek retaliation against Marín or to seek to stop Marín because Cuellar believes that Marín's family may come after him. The mere fact that Cuellar exclusively targeted members of Marín's family does not, as Marín argues, mean that the only logical inference is that kinship ties, rather than the desire for retaliation or deterrence, prompted Cuellar's threats."
The decision betrays a fundamental misunderstanding of family-based particular social groups. Cuellar's anger against Marin and his family was directly tied into their kinship ties to Marin's father, who Cuellar murdered. Thus, but-for Marin's kinship ties to his father, he would not have been targeted. It's important to remember that Marin was not required to show that his kinship ties were the sole motivation for Cuellar's persecution, only that it was one central reason for the persecution.
The full text of Marin v. Lynch can be found here: