Indian traditionaly have 7 Seers
The earliest list of the Seven Rishis is given by Jaiminiya Brahmana 2.218–221: Agastya, Atri, Bhardwaja, Gautam, Jamadagni, Vashistha and Vishvamitra followed by Brihadaranyaka Upanisad 2.2. 6 with a slightly different list: Atri, Bharadwaja, Gautama, Jamadagni, Kashyapa, Vashistha and Vishwamitra.
Buddhist text replaced them but Kashyapa stayed the same name
The 7 ancient Seers became in EBT
Buddha is the offspring of Adita. The goddess representing boundless. Who husband is said to be the sage Kashyapa. Then we understand why Buddha Kassapa represents the father of Buddha Gautama because it’s a way of saying he is in the lineage of Sages. And why it’s important that Buddhism teach that Buddha Kassapa was the one who was our current Buddha Gautama Teacher of the past life. There is even the tradition that he confirmed he will be the future Buddha.
Just like a father giving a inheritance to a son. Or like a father giving a blessing to a son.
Stories of sage Kassapa in Indian text is inconsistent but
Some texts describe him as son of Marichi and a descendant of the solar dynasty
He married Aditi, with whom he fathered the Adityas
Kashyapa is the brother-in-law of Dharma and Adharma
Kashyapa has sung the hymn in praise of Soma in Rig Veda (9.114.2).