Sucking lady just no way - sets her mouth up for fucking like an orifice! The passionate lady knows how to work her lips and tongue, not work her cock hole! To put it mildly, that's what a rubber doll can do. And in bed he just lies there and enjoys it, while the passionate woman assiduously wiggles in time with the cock.
I can see it's not the first time they've had sex together. It's so convenient - you don't have to take anyone off, there's always a shower and a bed nearby. Of course, her brother's dick is great, so any sister would fall for one and suck it at the first opportunity. Well, it seems to me, he doesn't mind having fun with his sister with it either - his own soulmate won't betray him or make him marry him. It was so cute when her brother came inside her - it just cheered them up. )