whether...or...充当并列连词的功能

Even in houses where there's enough space for everyone to sleep in their own bedrooms, children often share, whether because an adult has decided to free up additional rooms for guests, or siblings have said that they would prefer to be together.

whether...or本是从属连词，却连接了从属连词because引导是什么原因状语，起到了并列连词有哪些用途，请问这是语法错误吗

whether 可改为either。也可以讲解为whether后省略了it is, it指代主句内容，谓语动词为be，主语和be同时省略。