Board Thread:Dark Souls II/@comment-68.119.65.67-20140321002944/@comment-24684538-20140321022240

Did you kill 50 people in the arena and invasions combined? Because I don't think they stack, they don't for Blue Sentinels (with assistances rather than invasions) so I doubt they do for Brotherhood of Blood. Otherwise it's most likely a glitch like Kickface said.