Callias II in Wikipedia
Callias (Greek: Καλλίας) was the head of a wealthy Athenian family, and fought at the Battle of Marathon (490) in priestly attire. His son, Hipponicus, was also a military commander. He is commonly known as Callias II to distinguish him from his grandfather, Callias I, and from his grandson, Callias III.
Some time after the death of Cimon, probably about 445 BC, he was sent to Susa to conclude with Artaxerxes I, king of Persia, a treaty of peace named the Peace of Callias.
At all events, Callias' mission does not seem to have been successful. He was indicted for high treason on his return to Athens and sentenced to a fine of fifty talents.
Callias in Harpers Dictionary of Classical Antiquities
（Καλλίας) and Hippon īcus (Ἱππόνικος). A noble Athenian family, celebrated for their wealth. They enjoyed the hereditary dignity of torch-bearer at the Eleusinian Mysteries, and claimed descent from Triptolemus. The first member of this family of any note was the Callias who fought at the battle of Marathon, B.C. 490, and was afterwards ambassador from Athens to Artaxerxes, and, according to some accounts, negotiated a peace with Persia, B.C. 449, on terms most humiliating to the latter. On his return to Athens he was accused of having taken bribes, and was condemned to a fine of fifty talents. His son, Hipponicus, was killed at the battle of Delium in B.C. 424. It was his divorced wife, and not his widow, whom Pericles married. His daughter Hippareté was married to Alcibiades. Callias, son of this Hipponicus by the lady who married Pericles, dissipated all his ancestral wealth on sophists, flatterers, and women. The scene of Xenophon's Banquet, and also that of Plato's Protagoras, is laid at his house.