Planet Jupiter, one of the nine planets, Navagraha.
Brihaspati is the preceptor (Guru) of the Gods. One of his names is just Guru.
Shukra, Venus, is the preceptor of the demons, although he is not a demon himself.
Brihaspati was married with Tara.
Read about Brihaspati here
http://www.sushmajee.com/shani/1-kathaa-1-19/5-brihaspati.htm