Like others have said, DO NOT CANCEL YOURSELF. You will be penalized in more ways than one way. Your:
-listing visibility will be affected negatively,
-super host will be removed, and I believe you won't be able to regain the designation for another year,
-profile under review will state "host cancelled 5 days before reservation. (which may make other guests nervous about booking with you leaving you with more income loss)
Airbnb may be requiring proof of whatever he is claiming is his emergency. If he can't produce it, he needs to find other means of getting his reservation cancelled, this may be why he is insisting you cancel on your end.
I would highly recommend you keep all communications via bnb messaging system that way when he or you call airbnb they can reference what each of you have said.
Since your listing has been blocked for the dates he was scheduled to stay since he booked, you may have lost the opportunity to have other guests book. I think what some previously suggested is fair.
Let Airbnb handle the cancellation portion with him. Tell him as soon as he does that, Airbnb will "unblock your calendar for the dates he was scheduled to stay with you." At the end of the 35 days, you are happy to refund him for any amount you were able to rebook with other guests.
Hope this helps. Let us know how it turns out.
Dear XXX,
I am sorry to hear about your family emergency. Unfortunately I am not able to cancel your reservation. Please contact Airbnb directly to inform them of your emergency. They will take the appropriate steps to process your cancellation and refund.
As far as the additional refund, as soon as you cancel, Airbnb will unblock the dates for your reservation. Should I be able to rebook for any of the dates of your reservation, I will follow up with Airbnb to provide the refund. I will follow up one day after your scheduled check-out to confirm the refund amount should I be able to rebook. Thank you for your understanding. I hope your family member has a speedy recovery.