I'm not going to replicate the long family tree discussion here, so (snip)...

With that said: Hild's first couple of words upon seeing Belldandy and Skuld 
are "Ano hito sokkuri!", or "(You look) just like that person!" Of course, 
who "that person" is is not mentioned, but the implication is that 1. "that 
person" is Skuld and Belldandy's, but not Urd's, parent and 2. Hild knows him 
or her (father or mother?) well. Considering that Belldandy and Skuld are 
full goddesses, both of their parents must be gods. It is reasonable to 
assume that Hild would not be overly familiar with any god except an 
extremely powerful one, or even "her counterpart". 

Later, in chapter 136, Belldandy asks Hild if she can ask her something. Hild 
anticipates the question is "Doushite wakaretakatte koto?", meaning "Why (did 
we) split?" Again with the assumptions (and assuming is dangerous business), 
it is reasonable to say that Belldandy would have a personal interest in such 
a question if Hild guesses this. This coupled with the "Ano hito sokkuri!" 
implies that kamisama is Belldandy and Skuld's father, and that he is also 
Urd's father, with Hild being her mother. For whatever reason, the two split. 
This sort of pattern is not uncommon in mythology, and by pattern I mean man 
and woman are together, man splits from woman, woman and man now in direct 
opposition. Putting kamisama and Hild as Urd's parents might be weird, but if 
anything, it explains both her immense power and her lack of focus (which 
relegates her to second-class goddess status).

For these reasons I choose to assume, until otherwise proven, that "kamisama" 
is indeed the megami-tachi's father and that Hild is Urd's mother. Of course, 
there is no proof; merely evidence suggesting this is one of many 
possibilities. Curse the Japanese language's ability to leave out pronouns at 
whim...

Edward Chang, Skuld no Shinpu
Founder of the Coalition Requiring Animated Peorth
"Atashi tte yappari tensai!" -- Skuld
http://nekomikodai.otakalypse.com