查看移民局官方网站,貌似表兄弟姐妹,不在176担保的亲属范围之内:
You or your partner must be related to your sponsor as one of the following:
a non-dependent child – including a stepchild
a parent – including a step–parent
a brother or sister – including a step-sibling
a niece or nephew – including a step–niece or nephew
an aunt or uncle – including a step–aunt or uncle