They don't.
This is all they say in PPR.
"Should any of the following circumstances apply to you or any accompanying family member, you must inform this office immediately:
Change in marital status, for example due to marriage, divorce, legal separation, annulment or death of spouse;
Change in family composition, for example due to adoption or birth of a
child, including a child born to your accompanying dependent child
Death of principal applicant, spouse, accompanying children, or death of sponsoring relative;
Change in health;
You or any of your accompanying family members being charged or convicted of a criminal offence
Change in contact information: mailing address, e-mail address, or telephone number.
Your failure to inform IRCC offices of any of these changes may result in the cancellation of your permanent resident visa and may render you and your accompanying family members inadmissible to Canada.
Your failure to declare all of your family members, accompanying or not, will permanently exclude them from sponsorship under the Family Class regulations."
