Severus Snape had come to the conclusion that the Brothers Black sole purpose in life was to torment him. The one seemed determined to tease and frustrate him till he snapped, while the other seemed determined to, well, tease and frustrate him till he snapped.
He was fairly certain, at least, that Regulus didn’t realize he was doing it.
In fact, Regulus went out of his way to be nice to him. Smiled at him when they passed in the corridors, and sang his praises a little too enthusiastically, every time Avery and Rosier wavered over whether or not his skills with a cauldron were enough to make up for his lack of money and lineage.
Severus didn’t much care if they decided it wasn’t, was more than used to being relegated to the sidelines, but it didn’t grate as much as he supposed it ought, having someone younger stand up for him. Someone who was a Black into the bargain.
It helped that Regulus seemed to mean it. Cornered him in the common room to ask for help with his potions homework, and sought him out at the library, apparently content to sit quietly beside him rather than snigger and gossip with the rest of the dullards from the fifth form dormitory.
Sweet talked Slughorn into making Severus his tutor, and giving him extra credit for it, though the man still treated him like an idiot. Let them use his classroom only to supervise too closely when Severus tried to explain the importance of wrist action. Hovered annoyingly when he gave Regulus a demonstration, as though he was going to start ladeling draught of peace all over the classroom floor or something as equally stupid.
“We should take this somewhere more private,” Regulus told him a few sessions in, all furrowed brow and confessional whisper, and, in hindsight, it was probably that suggestion which was his undoing.
Because without Slughorn’s presence, his beady eyes and his interruptions, Regulus wasn’t at all bad to be around. Could be quite funny when he wanted to be, and when he didn’t Severus wasn’t disappointed, not when the other boy turned big blue eyes on him and explained how important it was that he did better in his O.W.L.s than Sirius.
They bonded over Black the elder's innate gitishness, swapped stories about his propensity to hex first and be given detention later, and though he didn’t see it firsthand, Severus later heard all about the vocal argument the brothers had got into, over suitable friendships and Hogsmeade Saturday companions.
It made Regulus’ awkward invitation all the sweeter, made the sickened look on Sirius’ face all the more satisfying, and from there it was only ever going to be a slippery slope past the point of no return.
They spent time together, too much of it, and one night it hit him that he was enjoying watching Regulus’ studied look of concentration more than he was the creation of a perfectly executed potion. That wasn’t a good sign, could never be a sensible development, so of course he took to seeking out Regulus’ company out himself, uncaring of the dangerous gossip which spread about the Quidditch changing rooms.
He stood up for Regulus, in turn, when Lestrange and Wilkes claimed he would never be dedicated enough to the cause, and wasted long hours visiting him in the infirmary, after a spat outside Arithmancy.
“If you were any good at the subject you would have seen it coming,” Severus said when he was finally discharged, still unsteady on his feet and a little too pale. Regulus only pulled him by the arm, urged him around an abandoned corner, and planted a kiss on his lips, chaste but determined.
“You can’t predict everything,” Regulus told him then, anxious like he wasn’t sure he wouldn’t be spending another night in the infirmary his troubles. Severus didn’t quite understand why, even as he kissed him back, less chaste and just a hint of desperate.
Some things were always going to pan out a certain way, no matter how one fought it.
It was inevitable.