On father demise intestate his 50 per cent share would devolve on your mother , you and your sister
2) if you and your sister had executed relinquishment or gift deed your mother would be absolute owner of the property
3) your mother can insuch a case bequeath entire property to you
4) your sister would not have any share as she relinquished her share in favour of mother
5) cousins would not have any share in the property