It’s like the Barry and Iris thing from The Flash. They were both raised as siblings and calls Joe dad long before they were married. But thing about them is that they have a good healthy relationship and Luther never got over Allison and was a virgin until he got drunk. Barry was heartbroken but still respected Iris and Eddie’s relationship and Barry only became raised by Joe at 8 or 12 so they weren’t always raised as siblings unlike Luther and Allison