Answer
The name Philadelphus bestowed upon Ptolemy II signifies a profound bond of familial love and unity, alluding to his unwavering devotion to his sister-wife, Arsinoe II. This title, meaning "sibling-lover", serves as a testament to their exceptional relationship, showcasing the deep affection and respect they shared. Philadelphus embodies the essence of fraternal love and marital harmony, celebrating the strength of their familial ties that transcended conventional societal norms.