Dependent child

Hi,
I am marrying a Canadian citizen and we want to applying for incountry PR. I have a son from a previous marriage who will be 18 on April, 2007. I know he needs to be included in our application. Even though we are very close he said he has no interest in ever coming to Canada for immigration purposes. He says he will not take a physical and knows he can never come under sponsorship. He also has a heart problem that he had surgery on when he was 5 yrs old and said he would never go anywhere else if he should need treatment. My ex-wife, still a good friend, says she will be happy to write a noterized letter with me that states he will not take the physical and knows the consequences. Does any one have any suggestions or ideas? Thanks for your help. Cwolf241