Imagine Sirius smirking at his little brother because Walburga just screamed to him and she suddenly says "Are you serious?" And he's like "No, I'm Regulus." And in the background you can hear Sirius laugh and they both end up punished but Sirius is so proud of his little brother because that was hilarious.
Now imagine little Sirius and Regulus started joking with his name after that and Walburga is just so mad at them, so she starts calling Sirius by his middle name, and every time she calls "Orion!" both her son AND husband answer her. At this point she even questions why she named him that.
So now she talks with her husband complaining about Sirius and says "Orion is just insufferable" and her husband looks so offended and the question just spilt her out of sarcasm and she says again "Are you serious?" Like a rhetorical question but her husband looks at her two sons in the eye with a grin and says "No, I'm Orion"