Palawan cherry is actually a paradox. There are certain aspects of it being argued and one of it is its name. For one its common name is a misnomer. The Palawan cherry is not a close relative of the Japanese cherry blossoms, but it is actually nearer in association with the legumes or the likes of acacia, narra, kamatsile, ipil and tindalo. Why it was named such is that it flowers fully with pink blossoms covering the whole entirety of the tree, much like a cherry blossom. Cherry blossom (several species of Prunus - we have native Prunus but not as showy as the Japanese counterparts) could not grow in tropical climates like in the Philippines.
Field botanist Leonard Co tells us that balayong is Cassia nodosa, a species native also to the island of Java, in Indonesia. In fact Mr. Co also states that Palawan cherry is not a native but rather prehistorically introduced to Palawan. But on the other hand, Dr. Madulid's Plant-cyclodia states that it is Cassia x Palawan Cherry, x meaning it is a hybrid between two or more species, a none pure species. I am not certain which species are claimed to be the balayong's parents, but most probably if this is factual, the Cassia nodosa is prime suspect.