Xbooru - 2010s 2018 2boys 2d 2d (artwork) anal animated skeleton big dom big dom small sub bigger dom bigger dom smaller sub bigger male blue penis bottom sans bottomless bottomless male brother brother/brother brother and brother brother penetrating brother brothers clothed clothing dominant dominant male duo ectopenis fontcest from behind position gay sex glowing glowing genitalia glowing penis incest larger male male male/male male focus male only maledom malesub monster orange penis papyrus papyrus (undertale) papysans penetration penetration from behind penis realdemdemdmensfw sans sans (undertale) seme papyrus sex sex from behind simple background skeleton small sub small sub big dom smaller male smaller sub smaller sub bigger dom solo focus submissive submissive male top papyrus uke sans undead undertale undertale (series) unseen male face video games white background yaoi