Ace and kinemon were friends/rivals and ace helped kinemon strengthen his fire cutting style and kinemon showed how to make that hat for oars jr , whitebeard tried for years to recruit kinemon but he had to look after momonosuke after his wife died ( was secretly killed by the villian in wano country a shogun warrior fuedal lord type character) whitebeard being about family understood and that's why he made wano part of his territory (even though it's a closed off land)
I`d like to see that come true