Bang, i know that's a super sensitive topic for you but look at it objectively.....
When Kaido announced in the last chapter he wants Yamato to be the next shogun, WB was there too. Both are on equal standing but he didn't say "our child"......
On the other hand, Black Maria is UNDER Kaido (i am only talking about hierarchy here) so it's no wonder Kaido would not mention about the mother coz that's irrelevant in his speech at that moment