Find them in your newsfeed or on a posting they’ve made (or in your friends list), as you hover over their link, a popup shows them as “Friends”, there is a menu item under that to “Unfriend”.
You can also just stop getting their news in your feed, by unchecking “Show in News Feed.” If they are relatives, that might be the most prudent option since then you can still go over there and see what they are up to without having it in your face every single day.
Thanks. It was just an ex girlfriend of one of my sons who’d just posted one too many stupid “I vote my crotch” statuses, who was just delighted that Mitt lost. Don’t need that in my face any more.