In some suttas like SN 22.95 and Snp 4.14, the Buddha is called the Kinsman of the Sun (ādiccabandhu).
Why is he called the Kinsman of the Sun?
What is the origin of the term?
Good question. I don't have any pali references at the moment, but there is this concept of solar dynasty.
... Buddhist texts include Shuddodhana, Gautama Buddha, and Rahula in their accounts of the Ikshvaku dynasty