If they have been accepted as a refugee in the US they no longer have a valid reason to claim asylum in Canada. If they applied for a refugee claim in the US, they would be denied and returned to the US as they cannot apply as a refugee if they have applied anywhere else. If he marries someone with a PR in process and the person applying for the PR does not include them in the application prior to landing, they can never be sponsored.
As you have been previously told being disabled during covid are not grounds for asylum for US citizens in Canada and you’ll be returned to the US.
