My youngest nephew has ridiculously curly hair and it's so soft and bouncy and adorable, right
Now I can't stop thinking (I put down fem!Reader bc that's relatable to me. Feel free to imagine this with any other kind of reader)
Running your hand through his curls, mesmerised. He feels self-conscious bc he was always taught his hair is messy and needs taming, etc, but the curls give it character and uniqeness, and you make sure to let him know in your own way.
He always seems to be trying to flatten the curls, even subconsciously, and everytime his hand reaches up and you see he's uncomfortable, you take him aside and tell him how amazing he looks with the curls and how it suits him - you shower him and his curls with love and compliments till the point where he's a flustered, blushing mess who can't put 2 words together.
(My hair starts out frizzy when I put it up, and the longer I leave it be, without combing it, it curls up just like my nephew's. I told my sister-in-law that he's the next kid in my side of the family to have curly hair after me, cause all the other kids, his older brother included have straight hair which is adorable in its own way, but curly haired children? One of my cousins has adorable ringlets, though, and her two older sisters have such straight hair. Honestly, it's a beauty. They're uniquely adorable, in my honest opinion.)
Regulus loves curls on other people but doesn't seem to like them on his own head. He strokes your curls lovingly, wrapping them around his finger, then letting go, chuckling a little when they go even curlier than before. He's one of the only people you allow to touch your hair.
His curls are so bouncy. Sometimes, when you're sitting with him, you'll reach up to boop his curls gently, giggling when they bounce back up and at how soft they are.
You once asked him for what conditioner he uses because damn those curls are silky asf!!! He refused to give it, saying it's a family heirloom and that if you wanted those curls, then you'd just have to stick with him. (He partially said this because he feared that you were only with him for this. He always fears that you will find someone or something better [Sirius] and leave him indefinitely, and at this point, he's too attached to let you go.)
You stay, but it's not because of the curls. You stay for him. And you tell him that too. It isn't until he realises it through your actions that he comes to understand exactly how much you care about him.