Urd's father. The easiest way to describe him is to simply say, "The Almighty" which in turn means "God." While we don't see anything of "The Almighty" in the Manga, we do see a little bit of him in the Anime OAV series. Obviously, he's the father of Urd, Skuld, and Belldandy, only he gets involved with a demon at some point (???). Why he does, I have no idea.
Urd's mother. Her name is Hild and she's the leader of the Underworld's systems. She bosses Mara around in the Manga and makes life as miserable as possible for the goddesses; not seeming to care if Urd is caught in the middle. Hild wants the love and affection of Urd, but unfortunately, Urd detests her demon side and acts rather icily towards her mother, who she doesn't refer to as "Mom." Hild enjoys cute things and is good at video games, just like Urd.
Urd's younger sister. Belldandy is a sweet, gentle, and loving goddess that Urd seems to get along with just fine. Urd keeps a watch out for Belldandy and constantly tries to assist her with her 'slow moving relationship.' She persistently stays on Keiichi's tail about 'making a move' on Belldandy. Urd is really the only one who understands the different emotions that Belldandy feels in her relationship with Keiichi, so often times, Urd is counseling Belldandy in 'the ways of love.' While Belldandy and Keiichi are often the guinnea pigs for Urd's crazy love potions, Urd always (well, most of the time anyway) has good intentions.
Also Urd's younger sister. Urd doesn't get along as well with Skuld as she does with Belldandy. Skuld is the center of Urd's teasing and taunting. Whether it be because she's a second-class goddess who can't use her powers, or because her breasts are too small, Urd can always come up with something to torment Skuld about. However, deep down, Urd cares immensely for Skuld, and many times, does her best to make Skuld happy.