#kouros

Kleobis and Biton, twin Kouroi (plural of kouros) statues by Polymedes of Argos (plinth inscription) dedicatied to Delphi ca. 580 BC. by the city of Argos Marble H 197 cm (6 ft. 5 ½ in.) Archaeological Museum of Delphi

"who is happiest (ὀλβιώτατοϛ) among humans?"

The meeting of Solon and king Croesus (Herodotus 1.29–33) is placed prominently at the beginning of the Croesus story and near the beginning of the whole work The Histories of Herodotus, completed 2nd half of 5th c. BC

Solon’s reply to Croesus:

Tellus (1.30.3–5): the happiest man is the one who has the greatest number of good things [big family included] through his life and then dies well (32.9). Solon chooses Tellus as happiest because he has both enjoyed continuous prosperity in a free country and died well.

Cleobis and Biton are second happiest, because of their glorious death when they expired after urgently transporting the heavy carriage of their mother-priestess during goddess Hera festivities (1.31); A good death is an essential element of the happiest life, and a crucial element would be lacking if the death were not good.

When Cyrus defeated Croesus and was ready to burn him alive, impressed by Croesus' cry "Solon, Solon, Solon!" allowed him to explain, heard Solon’s story, spared the life of the fallen king and honored him thereafter.

(PDF) Cleobis and Biton (Herodotus 1.31) [academia.edu]

https://www.perseus.tufts.edu/hopper/text.jsp?doc=Hdt.+1.32