Complex sentence: Nesbitt is the subject of Sheeran's songs, "Nina" and "Photograph", while the majority of Nesbitt's album, "Peroxide", is about Sheeran.
Split into simpler sentences: Nesbitt is the subject of Sheeran's songs, "Nina" and "Photograph". Most of Nesbitt's album, "Peroxide", is about Sheeran.