Is sibling consent needed when selling the property

My mother did not posses any property. I was working in another city and therefore to secure her, I bought a vacant plot in her name. 100% financed by me. I built a house on it which is again financed me. My mother has also made a affidavit stating that the property has been financed by me and the other siblings do not have any rights on it. Now 10 years have passed and now I wish to sell the property for which my mother is happy to sell it. When I sell the property, is it compulsory to get the consent of of the siblings(3 sisters) ? The buyer is insisting on the consent of all the siblings but I don't feel there is a need because it is not a ancestral property nor self owned by my mother. It was financed by me, an affidavit is in place and my mother is also happy to sell. I have s strained relationship with one of the sisters and can't get her consent. Can you please advice if sibling consent is compulsory in this case or not? Thanks in advance, Regards Omprakash