Hi please refer to this article for help on this issue: https://turbotax.intuit.ca/tips/who-can-i-claim-as-a-dependant-on-my-tax-return-6646
This link may also be helpful: https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/line-30400-amount-eligible-dependant.html