Janus was also the father of Tiberinus and Fontus.
Janus was really like the god of war for the romans. When the door was closed, they were at peace. But when it was open, they were at war, conquering other empires. This was really the rule for Romans for awhile.
So, in conclusion, Janus was the god of god of beginnings, gates, transitions, time, duality, doorways, passages, and endings. He used his powers (in the romans point of view) to start war, and end war. He had shrines built for him. He had 3 wives, and 2 children. He looked in to the future and in to the past, so he was viewed with 2 heads. You couldn't really view him with having a good or bad vibe.