I think this is "The Great Lie". Mary Astor is a concert pianist who refuses to commit to George Brent ("Peter") since it would interfere with her career. So he marries Bette Davis. But then he dies in a plane crash. And then it turns out that Mary is pregnant with his child. So Bette raises it as if it were her own. But then it turns out that George isn't really dead after all. So then both women want him and they want the child as well. And then it starts to get really complicated...They don't make them like this anymore.