Girls want to be models, so they're ready to get on any dick that will get them a job in the modeling business. To suck or not to suck penises - such a question does not exist for them. Everyone sucks - just not everyone flaunts it. But not all of them are willing to let you work on your sweet pussy. At least the girls should be given time to get naked. There's no time to think about it. You got to ride the dick.
It's not even quite clear whether the brother helped his sister, pleasured her, or taught her. Either way, she should be grateful to him after a fuck like that. It's funny to see how he uses both his phallus and her toys to develop his sister's anal hole. It's bright and exciting, and you can see the details that are so valuable in a process like this. I wonder what he will turn her on with next time.