Is it normal for my sister to tie me every sunday?

I know my one niece woke up with her sister using a

dildo( sex toy) on her at first she was scare, angry but

after she started fucking her with it my niece wanted the

dildo all time and yes they do use it on one another when

the 20 yr old comes home from college they engage in lesbian sex

the one niece whose age 20 goes back to school in the fall

and her sister is age 18 and will graduate this coming year

so she's a Senior in her last year of High School.