[557] **By the Buddha, the Kinsman of the Sun (buddhenādiccabandhunā):** "By the Buddha (buddhena)" — he who is that Blessed One … this designation (paññatti), namely "Buddha," is a designation based on realization (sacchikā paññatti).
"The Kinsman of the Sun (ādiccabandhunā)" — "ādicca" is a term for the sun (suriya). The sun is Gotama by clan; the Blessed One too is Gotama by clan. The Blessed One is a clan-relative of the sun, a kinsman by clan. Therefore the Buddha is the Kinsman of the Sun. Hence, "by the Buddha, the Kinsman of the Sun."
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.