1) grand children consent was not necessary to transfer property in name of children
2)father was free to sell his share in proeprty
3) it is not fraud at all . it is not ancestral property
4) your mother has right to stay in her matrimonial home
5) she can seek injunction restraining sale of property
6) your mother can seek maintenance for herself
7) your mother can file case of bigamy against her husband and his second wife under section 494 of IPC