Desperately need to talk about how fatherhood works in the Mahabharata for Surya and Indra with their mortal sons.
Arjuna is known as Indra's child. His most common epithets (related to familial lineage) largely come from his mother, but it is openly understood that he is Indra's child. Indra helps him out so many times and it's wholesome as hell.
Then you have Karna, who is not acknowledged as Surya's son, and Surya keeps Kunti's secret either out of duty or regret (for leaving a child with a baby, that is). So his help is next to nothing for most of Karna's life. And then the event comes when his brother is about to take away his son's armour, the only protection he has been able to offer this boy, and he knows Karna will give it away but he goes to dissuade him anyway. When he comes, in most versions, he says he comes to aid an ardent devotee. In BORI he says that there is a secret he cannot reveal, but he is here to warn Karna out of love.
And it stands out to me so much, that from Karna's perspective, he meets his father through years of devotion and prayer, because you can tell he thinks of Surya as his mentor and spiritual guide, and Adhiratha as his father. He has next to no qualms in claiming Radha as his mother even after he is told the truth, and his reaction to Kunti being his mother is not dissimilar.
And then this god shows up, does not even bother to reveal that he is his father (I imagine Karna must have been pretty peeved when he found out - in a "you could've just told me when you visited" way) and asks him to let go of the one thing he takes great pride in. Even there too, there is a great deal of respect for agency: Karna is firm and Surya compromises. If they'd had a few more chances to interact, I think they would work out pretty well.
And then you have Arjun and Indra, so beautifully entwined, so beloved and so dear. Indra helping Arjuna is seen as interference (and rightly so), but there is something so paternal about how Indra desperately tries to protect his child - depending on the version he (not necessarily chronologically):
a) mitigates the Urvashi curse,
b) sends out the Gandharvas to heckle the Kauravas
c) bestows divine counsel upon his son
d) gives him a great bow after getting thrashed
e) turns into an insect and gets Karna cursed.
And most importantly, he shows up at a MORTAL'S door, CLAIMING TO BE A BRAHMAN (which is, again depending on version, one of reasons why said mortal got cursed), declines offers of land and money and girls, and shamelessly demands the armour. A KING. REDUCED TO A BEGGAR.
Because remember, technically Brahman's are given state funding for their research, education, priesthood, or simply their birth. Indra does none of these. He knows this. Karna knows this. He knows that Karna knows this. But he demands it anyway.
Obviously, Karna's devotion to the Sun God, and the fact the said god is his father is a narrative device meant to represent his arc of reaching for the sun and getting burned (in most cases, at least), while Arjuna's relation to Indra and his rain motifs is because narratively he peaks at terminal velocity and then freefalls to the earth as soon as Krishna dies.
But I love thinking of what their respective relations to their fathers must have been, and how it mirrors/contrasts Kunti's relationship with the gods. Kunti calls Indra and he does what she wants (for him to give her a baby), and is able to support their child in most cases. Surya is called and he does not do what Kunti wants (for him to leave immediately), and his relationship with their son is one of distance and endurance. But they are good fathers still, as good as god can be. (Except Surya with Shani. Idk what's going on there).
Anyway I forgot what point I was trying to make... but yeah!