I too agree with the above posts.
There was a hint in a case last year that the Federal Court might consider H&C reasons for not fully enforcing this, but I do not recall specifics, and in particular I do not recall the ultimate outcome in that particular case -- it may have been no better than a suggestion that the law should allow some H&C exceptions, but currently does not. As in, not much on which to pin any hopes.
If you can readily afford a lawyer (not merely a consultant), you can take the particular details of the situation to the lawyer for a consultation. Most lawyers will be frank and honest as to whether there is a viable approach or not.
For context: I have seen cases in which, after becoming a PR, a father alleged he only found out about a child of his, from an earlier casual relationship, before applying for PR, and even in that situation the father was not allowed to sponsor or otherwise bring the child to Canada despite the fact the father did not have the information to provide CIC at the time of his application.
In other words, while many rules and laws often allow for some exceptions, the government tends to enforce this one (requiring all dependents be declared and examined, even if non-accompanying, otherwise they are forever barred) very strictly.
