Just suck it up and flush your toilet from a ways back. Like your foot or something. I was sensitive my First trimester too about things likE that. But if you'rE trying to Fit in... Don't say anything, it'll make it worse. Let your boyfriend know jokingly or lightly.. and see how he takes it.
I should but Its just weird to say it u no.. I really have trouble abt speakin up
Talk to your boyfriend about speaking to his family. It will probably go over better if he says something.