Connabeth can actually be soooo funny when looking at it through the lens of how some people (looking at you Kai) hc Luke to feel about his demigod siblings.
Like, he ran away from home because his mother was dangerously unwell and his dad fucked off to leave Luke to deal with it. They're already off on a bad foot. Luke ran away because he was completely alone with May, who couldn't take care of Luke and who Luke couldn't take care of. But then he runs into Annabeth, who was similarly neglected by her family and felt the need to run away and he feels a kinship with her. He takes her in like his own little sister (or daughter, considering Luke calls himself the group dad in his diary) because they don't need their blood family, they have each other.
And then he gets to camp and is stuffed in the Hermes cabin with all the kids suffering neglect and he meets his half-siblings. It hurts to see all of Hermes' other kids and realise just how little Luke and May mattered to him. Of course he never came back to help May or take care of Luke, he was off making a million other kids. But everyone else is going through the same thing, so he just keeps his head down and gets on with life.
Until Connor. Because Connor isn't like the other Hermes kids. He doesn't just have a bunch of half-siblings in the cabin, Travis is his full brother, Connor is Hermes' second child with the same mortal. That's what Luke hates. Travis is fine, he can be explained away in a million different ways. But Connor was intentional. Hermes had to go back to the Stolls' mother for Connor to happen, which means he could have gone back to Luke and May, but he chose not to. Connor is living, breathing proof that May and Luke didn't matter to Hermes and Luke can't help but resent him for it. Luke knows it's not his fault, Connor had as much say in this as Luke or Travis or anyone else did, but it's what he represents.
Luke wanted so badly to mean something to Hermes, and he thinks he might have a chance with his quest. But then he fails, his face gets mauled, and he has to come back to camp to live in the overstuffed cabin with all his siblings, knowing he missed his chance to be important.
And then his adoptive little sister starts dating the embodiment of his familial insecurities and the source of his rage.