Alpheios

During a battle at Troy two sons of Diokles are killed. Now, remember the name Diokles.

...Then Aeneas killed two of the best of the Danaäns, the sons of Diokles, Krethon and Orsilochos, whose father dwelled in well-built Pheme, rich in substance. He came from the line of the river Alpheios, which passes through the land of Pylos, broad in its flow.

Iliad Book 5 line 548-553 Barry B Powell
Iliad Book 5 line 556-559 Barry B Powell

When the twin came of age, they followed the Argives on the black ships to Ilion with its fine horses, to bring honor to Agamemnon and Menelaos, the sons of Atreus. There the end of death concealed them.

Diokles lived on the border of Pylos by the river Alpheios, though this isn't part of Pylos anymore.

The sons of Diokles followed the brothers Agamemnon and Menelaos in war, which would suggest they didn't come from Pylos itself. They must have lived in one of Agamemnon's seven cities and more specifically one in Pherai, which means it can only have been Antheia, in the northern part of Pherai, the closest to the river Alpheios, lying just east of it. Agamemnon and Menelaos could have owned this part of Pylos for strategic reasons, connecting Sparta and Pherai by land, because the mountain range Taygetos is too much of an obstacle.