He kept Sirius from slinking down his body, using his mouth down there - he wanted to keep Sirius where their lips could meet and his tongue could taste. Severus wanted to drown all his senses in his lovers tonight. Very Snapey.
Once Sirius and Remus decided to coordinate clasps on the shoulder, brushes of knees, hands on arms and quick, there-and-gone-before-Severus-could-react cheek kisses, And very Sirius and Lupin!