Very dependent on the circumstances. You will need more than just a letter to prove that they are separated like records of different addresses during that 20 year period. Unfortunately some families do claim that parents are separated if there is concern that one parent may not pass the medical.Not necessarily. According to CIC’s website, “Legally Separated: This means that you are married, but no longer living with your spouse.” Some countries don’t have divorce so there is no way to file a separation with the courts. In my mother in law’s case, she hasn’t had contact with her husband for over 20 years so she wrote a letter explaining this.