1. If the said 2 legal heirs refuse to sign the settlement deed, then it will not be valid in the eyes of law.
2. The division of the property of your grandfather should be in to 5 parts, each for his 5 sons.
3. If any son was not married or died without leaving any wife or son and daughter, his share will not be counted.
4. Now, each share of the said sons, including the deceased sons, will be divided amongst their individual legal heirs being their wives and sons and daughters.
5. If any of the legal heirs are unwilling to sign the settlement deed validly executed, then partition suit can be filed by the majority legal heirs and get their shares separated and divided by metes and bounds.
6. Thereafter they can enter in to development agreement with any body they wish to.