Senator Kennedy -- often known as Ted or Teddy -- was the youngest of four sons born to Rose and Joseph Kennedy. known前面是否应该有is/was；born前面是否该有who is/was，是因为什么原因，如习惯等被简略吗？
Senator Kennedy -- often known as Ted or Teddy 此部分为主语，Ted或Tedy仅仅是指前面那个名字的人通常以这个名字而被人们所熟知，所以此部分为一个整体； was 为be动词，在本句中做句子谓语； the youngest of four sons born to Rose and Joseph Kennedy. 此部分为宾语，the youngest of four sons这部分是指四个儿子当中最小的一个，也就说明了主语的身份，而后面的仅仅是补充说明是Rose and Joseph Kennedy他们的儿子而已。