Complex sentence: Her elder brother has a "little sister complex" and will do anything for her; he feels his sister is truly noble, and would do anything for her, and is often moved to tears by the smallest acts on her part.
Split into simpler sentences: Her elder brother has a "little sister complex" and will do anything for her. He feels his sister is truly noble, and would do anything for her, and is often moved to tears by the smallest acts on her part.