一个名词后可以有两个定语从句，这两个定语从句可以是并列关系（这时需要并列连词），也可以不是并列关系（不用并列连词）。

Tom is the man I talked about yesterday and whose father is Li Jiacheng.

两个定语从句被并列连词连接，共同修饰先行词the man. 

I like the tie you wear which your sister gave to you as birthday gift. 

第一个定语从句you wear修饰the tie。第二个定语从句which your sister gave to you as birthday gift修饰the tie you weat。由于这两个定语从句不在一个层次，故不用并列连词。

以上两种情况，通常第一个定语从句中作宾语的关系代词省略，第二个关系代词不可省略。