Hello, while waiting for more information, I submit to you a theory on which I work and which I really like.
My English is not perfect, I will do my best ^^
Kaido's son is a Rabbit (or something close to it (hare, mythical, whatever)
Which makes me think that is a succession of coincidence, or very subtle little details, but judge for yourself.
1) First of all, the image I put below, which appeared in the magazine Vol. 6 came out on May 24, 2019.
In this magazine, Oda reveals an extension of a plate from chapter 920, revealing alongside the calamities, a 4th little character.
The resemblance to a rabbit is I find it quite striking, in my entourage, all see a rabbit, without even know the context.
2) The chapter where Kaido announces having a son, went out in Japan on Easter Monday (you will say to me "Hey Lake, Japan does not celebrate Easter" that I would say to you that Oda always has great freedom on cultural references.
3)The few words of Kaido, "he will show his head at least?", Which one could in the broad sense, also say, "Get out of his hole / burrow", and which for me insinuates heavily that his son lives on the island, but that it shows itself very rarely.
4)The task of finding it and bringing it entrusted to the Flying 6. P1 and Drake have a predator FDD, I think the other 4 too. And the Rabbit is a prey, a ... game ^^. The promised reward also proves a not so simple task.
If we push further to some cultural reference (do not include it in the points cited above, I just show 2 other pretty coincidence.):
1)The hare of Mars, has the habit of having tea with the Mad Hatter (who is associated with Perospero, who is on the way for this banquet), attention I say not that they know each other, I just say that here is a coincidence, the son of Kaido and Perospero will be brought to meet in this arc.
2)The Lunar Rabbit (moon, Kozuki, Shimotsuki all that, names linked to the moon) In Chinese mythology, he is often presented as a companion of the goddess of the moon Chang'e, constantly making the elixir of long life for her, but in the Japanese and Korean versions, he beats the sticky rice paste with a pestle to prepare the mochi
Elixir of long life? (Law) Goddes of the Moon (Toki?) Mochi (Katakuri)
Simple coincidence I grant you, but still curious
I also think of a parallel with Oden, regarding the age of Kaido's son, but also a parallel to Jack, I think that Kaido's son the same age as Jack, or very close.
who knows, maybe an intrigue will turn the top since the son of Kaido must have been a similar age to Jack
On the one hand, Kaido's son who is in disarray, does not even show up at the biggest event in Wa, the fire festival.
the other, Jack, ready for anything, to face a country, a navy fleet, a thousand-year-old elephant, he takes pretty crazy risks for Kaido, he seems even at the moment the most involved for the image of his captain
Finally, if Redon is true, chapter 980 should therefore be released on Monday May 25 in Japan, the magazine volume 6 showing this shadow resembling a rabbit, was released on May 24, 2019 ^^
Thanks to those who read me, don't hesitate to give your opinion!