I was having the same problem when trying to phone the UK. Turned out that TOT have an option for customers to bar international calls. For some reason this had been applied to our landline. TOT sorted this out quickly and I can now use 001 or 008.
As others have said, if your brother has internet, you could use the LINE app or Watsap for free calls, including video calls.
I only use the landline for calls to the UK government agencies.