how do I group my leads for business in salesforce ?

Example: In a lead want to appear all contacts who work at the same company , it is possible ?

Good afternon, I am Igor, I need to create a good field to enter the CNPJ my leads, I've been giving a good searched and not found anything that could solve my problem I ask to help me, let her in my field CNPJ need when registering a new lead, when it becomes null so 00.000.000/0000-00, and when you get some value so 34.456.212/2341-98, I ask you to help me, thank you.

Good afternon, I am Igor, I need to create a good field to enter the CNPJ my leads, I've been giving a good searched and not found anything that could solve my problem I ask to help me, let her in my field CNPJ need when registering a new lead, when it becomes null so 00.000.000/0000-00, and when you get some value so 34.456.212/2341-98, I ask you to help me, thank you.