谁知道关于英语句子代词歧异的讲解

I know Jack and Tom but he doesn't know him.
不知道哪个“他”，就算个歧义。

I know more about her than him.在这个句子中，既可以理解；我了解她比他（对她的）了解得多；也可以理解成：我了解她必了解他更多。