Funny, when Lucien Lanchance told to my Thalmor Slayer Khajiit "The Keeper is a sacred position within the Dark Brotherhood. Ask yourself - do you trust the wisdom of our lady?" he replied "Tell the Night Mother that the only voice I listen are the voices of the Nords killed by the Thalmor, including my adoptive Nord parents, demanding more Thalmor blood." and he killed and soultrapped Cirero saying "I hope Sithis won't mind if you become the servant of the Ideal Masters now."
So yeah, I killed him and soultrapped him because he is annoying as Oblivion.