Are Freddie Aguilar and Florante Aguilar the same person?
No. Freddie Aguilar is a Filipino folk singer while Florante Aguilar is a classical guitarist. It is easy to confuse because both are Filipino, both play guitar although in very different styles, and both have a nationalistic streaks reflected in their work.
Florante Aguilar was born Florante Aguilar, thus his name is not a stage name. To compound the complication, there is also a folksinger named Florante de Leon who is also very popular in the Philippines.
Folksingers Freddie Aguilar and Florante de Leon are based in the Philippines and have made their mark in the 1970s. Their places secure in the annals of Filipino pop and folk music scene. While Florante Aguilar is US-based and making a different wave of his own.
It is purely by coincidence that Florante Aguilar's name is a combination of these two singers.