In the same link we already gave you, it says: If you claim to have language abilities on your application, you must provide conclusive proof of your level of proficiency. The keyword here is IF and that suggests that you could apply without claming any language skills.
Also the same page says this: Citizenship and Immigration Canada (CIC) officers will not conduct an interview to assess your language skills. CIC will only use test results from organizations approved by CIC in assigning language points.
However, even if something is allowed, it might not be a good idea. How is your cousin going to live in Canada without knowing English or French? How is he going to find a job and work with people? How is he going to rent an apartment, get a drivers license, buy a car, buy a house, do his every day shopping, banking etc. etc.? He will be open to be cheated on his lease, in contracts to buy things, at his work.. He really should be taking english or french right now to prepare.
