Complex sentence: Historians say that Şehzade Mehmed was very much like his older half-brother, Şehzade Mustafa and that he looked up to him as his role model, and had a good relationship with him since their childhood.
Split into simpler sentences: Historians say that Şehzade Mehmed was very much like his older half-brother, Şehzade Mustafa. He looked up to him as his role model, and had a good relationship with him since their childhood.