"Do you have any siblings?"
Yes, I had the same issue. It's pretty basic. AFAIK, any time you have a yes/no question, both "statement + 吗" and "verb 不 verb" should be accepted.
"你有沒有兄弟姊妹？" (using, "兄弟姊妹", a synonym for "siblings") is accepted—which is nice—but "你有沒有兄弟姊妹嗎？" (ending with "嗎") is not even though this is a "yes" or "no" question.
The 有没有 already serves to make this a question. Verb, negative verb is a common question form in Chinese and doesn't require the additional 吗 participle
If there is a 'you mei you' in the sentence no 'ma' is needed as they mean the same thing.