The people on this forum are just regular people
(mostly) like you and me and they have no real idea of the legality of the processes and the steps that IRCC takes internally when sharing data or conducting background checks. The actual lawyers who do understand that process here - like
@legalfalcon - may not provide this information on a forum and may require to be consulted off-forum.
However, you can start off your research by reading these links that show up on a simple Google Search - from the official website.
This is a link to the official instructions: According to this, they need to be able to prove that they have been together for at lesat 1-year before they can apply as common-law partners. The evidence from the Phillipines will indicate that they've been together in the past, but in the year immediately preceding their immigration application, they need to be able to prove that they are still together.
That may be a problem but a trained professional -
like a lawyer - might be able to tell you how to get through it correctly.
What you are getting on this forum right now is just "guesswork" or "beliefs" - none of which have any value in the real world. If something goes wrong, none of these people are going to have to deal with the consequences - your nephew will.
Here are some other important links:
How IRCC assesses Common Law relationships:
How IRCC assess Conjugal Relationships
Now, take this information, read it, understand it and go to an immigration lawyer - not a consultant - a lawyer, and figure out how to go about the process in the right way.
AGAIN - NOT AN IMMIGRATION CONSULTANT - AN IMMIGRATION LAWYER - cannot emphasize on this enough!