Complex sentence: According to "Shinra no kiroku", Morosue's grandfather, Iemasa, was introduced as the Lord of Shigebetsu castle and one of the Ezo shugos; however, one theory is Andō Sadasue, not Morosue, was the only shugo ruler of Ezo.
Split into simpler sentences: According to "Shinra no kiroku", Morosue's grandfather, Iemasa, was introduced as the Lord of Shigebetsu castle and one of the Ezo shugos; however. One theory is, Andō Sadasue, not Morosue was the only shugo ruler of Ezo.