I am in the same boat too, my parents are separated and I'm sponsoring my mom. Please read what I have researched below as this is my basis.
5.11. Inadmissibility and non-accompanying family members
All family members, whether accompanying the principal applicant or not, are required to be examined unless an officer decides otherwise. Normally, an inadmissible family member, whether accompanying or not, would render the principal applicant inadmissible.
There are, however, two exceptions to this rule described in R23. The first is the separated spouse of the applicant and the second is where a child of the applicant who is in the legal custody of someone other than the applicant or an accompanying family member of the applicant, or where someone other than the applicant or accompanying family member of the applicant is empowered to act on behalf of that child by virtue of a court order or written agreement or by operation of law.
Satisfactory documentary proof of a separation and of custody being with someone other than the applicant is required. A
separation agreement or custody papers
are examples of acceptable proof. Officers will not issue a permanent resident visa to separated spouses, common-law partners or children in the custody of someone else, even if they are examined. This is because
separated spouses and partners are not members of the family class as per R117(9)(c) and because children in the custody of someone else are non-accompanying family members.
Officers should be open to the possibility that a client may not be able to make a family member available for examination. If an applicant has done everything in their power to have their family member examined but has failed to do so, and the officer is satisfied that they are aware of the consequences of this (i.e., no future sponsorship possible), then
a refusal of their application for non-compliance would not be appropriate.
The intent of R117(9)(d), R117(10) and R117(11) is to ensure that persons whom the sponsor made a conscious decision to exclude (either by not declaring and/or not having the persons examined) from their own application for permanent residence cannot later benefit by being sponsored by this same person as a member of the family class.
Separated spouse
Where a spouse was not examined as part of the application for permanent residence because the applicant and spouse were separated and examination was not required, the spouse cannot later be sponsored as a member of the family class by virtue of their relationship to the sponsor. This was true under R4(2) of the previous legislation and it is still valid under R117(9)(d) of the current legislation.
https://www.canada.ca/content/dam/ircc/migration/ircc/english/resources/manuals/op/op02-eng.pdf
