Severus held himself steady with one hand, and forced himself not to grip the other boy's hip with the other. Jaw clenched from the effort it took not to bury himself in Regulus with one brutal thrust, he slowly guided the head of his prick into his lover's body.
"Fuck," Severus hissed as he breached the ring of muscle. Collecting himself, he murmured, "Let me know if it hurts too much, and I'll stop."
Gods but Regulus felt amazing-- hot, and tight, and perfect.