I just completed inspection contingencies for the property I am in the process of buying, and to my surprise, my real estate agent emailed me to consent to a dual agency contract.After doing a quick Google search, I discovered that this should have been disclosed from the get-go.

She's even replaced their kitchen's double oven with a better double oven without consent which she is currently paying the replacement costs. 

Does the living owner have sole rights to sell or do the children need to consent on selling? 

First, communicate your plan to the mortgage holder, securing written consent and checking the mortgage agreement for any restrictions.

However, any title search would disclose the existence of the land contract and smart lenders would require the consent of the contract purchaser in connection with the proposed transaction. 

It also then requires that the existing lender give written consent.

If a sibling had now deceased parent sign over property to them, without the consent of other family, is there any legal recourse?

Notice to the lender has caveats as to notice and asking them to deny consent or consent is assumed, but this is only a ploy to justify the position of a buyer, it may or may not work.As Brian mentioned, the due on sale can be an issue with either one.Lenders will generally treat an installment sale the same as they do with a lease, 75% of income to off set the debt.

Here is the clause.... perhaps you can amend your lease and/or use it in the future.AIR CONDITIONERS.Tenant agrees to not install or cause to be installed air conditioners without prior written consent of Landlord.

These lenders have strict protocols in place for releasing this info, not easy to get even if you have the borrower's written consent.