Any financing with a personal guarantee is unique to that party and consent by the lender will be needed for a buyer to assume the loan.

If the lease requires the owners consent it would appear you have no grounds.

Im not against options, just be careful, the reality is very few people exercise their option, like 2-5% (they just cant clean up their credit and save) and tend to forfeit their option money, even though you have a contract, do this a few times, and you will build a reputation, and not a good one even though what you are doing is legal, and everyone consented you will still be considered the bad guy for taking their option money.

(BTW, you can't wholesale a financed sale or Sub-2 without the seller's specific consent accepting the real buyer.)  ?

Our privacy laws are such that any one selling such a list would have to obtain the consent from those on the list .. which just is not going to happen at a high enough rate to make a business.You either need to build your own lists by canvassing a neighbourhood; watching the papers / Royal Gazette for mortgage sales / foreclosure sales / tax sales; or Spamming an entire neighbourhood (Canada Post provides such a service).

It is very likely that the seller listed it without full consent of siblings.

After a notice of default/demand is mailed out, the seller will not be able to contract on the property without consent of that lender, it is a notice of legal action and your contract can be squashed.

I know a guy who is renting his apartment to a friend who will be AirBnBing it with the landlord's consent. 100% of the proceeds goes to pay the rent, then they split the remaining income 90-10. 

Business Law 101, that's basic business law that is often taught in high school which very few wholesalers ever took, much less cracked a book on, that explains to you that:When a "partner" has the ability, the consent to contract on behalf of a partnership, that partner binds the other partners to that contract!

Silence generally implies consent.