Maija Both 😃
Joh Do you really believe they don't know you like to be submissive?
I have now marked both because @Joh is right. your parents know 100%, probably not for long, but at the latest when they have installed more and more devices and have noticed that your problems with it are not that big, they will have figured it out, i'm very sure
I would tell them that you have a preference for women, you're "under lock and key" anyway, so you don't have to worry. Start with something funny like "Mama, Papa You do not need to worry that I will be unintentionally pregnant"