Rating: PG-13
Author: Amidaala
Disclaimer: I don't own Star Wars. If I did, I would've put in some Obi/Ami.
Padme knew she would be having Obi-Wan's child, but also knew that she couldn't make him marry her. He could not and would not give up being a Jedi. Anakin, however, was willing to break the rules. He was willing to marry Padme. So Padme married Anakin, not only because she wanted to be married before she gave birth, but because there was a power in him that scared her- she didn't want to face the consequences of refusing him. Padme did not tell Obi-Wan that the child (or children, as we know) was his, because she didn't want him to feel like he had to quit his important role as a Jedi. Obi-Wan suspects it is his, but persuades himself to think it is Anakin's. He is not exactly as relieved at the thought of this- that Anakin is the father- so much as he is slightly jealous. And also, besides these feelings, he feels sorry for Padme if the child is Anakin's, because, after all, Anakin is inevitably turning to the dark side.
Obi-Wan is not the only jealous one- Anakin is suspicious that Padme has been or still is involved with Obi-Wan. This, combined with the fact that she isn't grateful that he's trying to save her life, causes him to take some of his anger on her- in the form of Force-choking her. Obi-Wan persuades him to let go, but then Anakin and Obi-Wan fight. As we have known since Episode IV, Obi-Wan wins. After this he helps Padme give birth to Luke and Leia- who, as he know knows, are his children. He was deeply affected by her cause of death- she had no will to live because Anakin, her husband, was a Sith and would probably kill her even if she did survive childbirth. He decided to make sure the children were raised well, by putting Leia in the care of the trusted royal family on Alderaan, and Luke in the care of his brother Owen and Owen's wife, Beru on Tatooine.