Who may co-sign
On a super visa application, a co-signer is a second person who signs the host’s letter of invitation and adds their income to help meet the minimum necessary income requirement. Only one relationship qualifies.
IRCC’s rule is that “Your child or grandchild’s spouse or common-law partner can co-sign the letter if they’re a Canadian citizen, permanent resident of Canada or registered Indian. Other family members of your host, such as siblings, can’t co-sign.” So the host’s spouse or common-law partner may co-sign and contribute income, provided they hold the required status; a sibling, cousin, or friend cannot, regardless of how much they earn.
Check status before you rely on the income
Families relying on combined household income should confirm the co-signer’s citizenship or permanent-resident status before counting on that income — it is the gate on the whole approach.