Izuna Uchiha died decades before Kakashi's father was born.
Try reading the chapter. He feels that Kakashi broke his dying promise to him by failing to protect Rin.Obito doesn't make sense, he saw Kakashi as a friend and his last 'dying' act was to give Kakashi his Sharingan as a token of their friendship and his desire to be helpful. To think that would turn in to such bitterness which would involve Obito going under cover, bringing together the world's worst/most powerful ninjas and obtain control of the Kyuubi due to some irrational childish angst seems unrealistic.