介词+宾语,但是than是连词,后边连接一个句子（句子成分常常可以省略.）
His brother is taller than he.就是用than连接了he is tall,省略了is tall.
His brother is taller than he.
His brother is taller than he is.
His brother is taller than he is tall.这都是formal的用法.
His brother is taller than him.是口语中可以用到的informal的用法.