主人公的堂表亲作为配角

One or more of the support characters is a [url=https://en.wikipedia.org/wiki/Cousin]cousin[/url] of the protagonist. A cousin is a relative with whom a person shares one or more common ancestors (other than a parent, child/descendant, sibling, child/descendant of a sibling, or sibling of a parent/ancestor). However in common parlance, "cousin" normally specifically means "first cousin".