shanks's relationship with the whitebeard pirates is soooooo interesting (dodging tomatoes as people shout you just want to talk about shanksmarco again!) cause he thought of ace (who he hadn't met yet) as a little brother. and he liked luffy so much that he gave that kid his hat, he saw so much potential in him. and then years later he finally meets ace and gets a little nibble at the back of his mind like, captain named his son after his sword?!
but ace wasn't looking for a connection to roger, actively resented him, and shanks isn't the kind of guy who'd force his perspective on others (that would, after all, make him just like a celestial dragon which is the last thing he'd ever want), so he doesn't bring it up. but he does his best to watch out for the kid who's (checks notes) going to try and kill whitebeard?!
but shanks, who grew up on the oro jackson and has personally gone after that old man, knows whitebeard. whitebeard did not instantly one-shot him and buggy when they had the nerve to try and attack him as teens. he knows ace is gonna meet that great pirate and get parented, which sounds like exactly what he needs. tbh. and when he gets the news about whitebeard's new recruit, a rookie who tore up paradise and hit the new world at breakneck pace, who then became his second division commander...
so this kid who's his little brother in spirit has been in the care of the whitebeard pirates for (i wanna say two?) years, and those are really the most capable hands he could've ended up in so shanks doesn't worry too much about him. until he goes after teach, who capably scarred shanks when he wasn't even off-guard. and then got captured by the marines.
and whitebeard, being whitebeard, mobilizes his WHOLE FLEET to go save that kid who is as good as family to shanks. and then LUFFY shows up-- which shanks probably only found out about after arriving at marineford. luffy, a rookie, would've died countless times throughout the war at marineford if the whitebeard pirates hadn't stepped in on his behalf and he still got majorly beat up...
it says a lot about shanks that he arrived to back up the whitebeard pirates at marineford, but it's also worth considering how much he thinks of the whitebeard pirates as having acted on HIS behalf in protecting ace and luffy when he couldn't be there himself. i think a lot about why he'd step in and handle whitebeard and ace's funerals, and even if we never find out anything else about his relationship to the WBPs, it's obviously because they've looked out for people who were important to him first.
it STILL doesn't explain why marco would LET shanks step in like that. maybe for ace, now confirmed to be the bio son of the man that shanks also considered a father, who disowned that father and now considers himself the son of a man who is also marco's dad... but that marco would step back and let shanks do that for whitebeard... that speaks to an immense amount of trust and history, which we have gotten ZERO of!! 😭 why was teach at mary geoise??? was the rest of the crew there as well?????? why is marco so sure that shanks 'isn't the type to do stupid things'??? WHAT HAPPENED!!!!