How can I receive larger portion of Inheritance sum?
You are not entitled to an inheritance. No one is entitled to an inheritance. If someone chooses to bestow a gift upon you when they die, then that is a blessing BUT you are not entitled to it. If your parents want to leave it all to the SPCA, the church, or the circus they can do it and you are just out of luck. And since you are looking for a way to cheat your younger sister out of her theoretical future inheritance, I hope that your parents leave YOUR theoretical future inheritance to some charity. GO TO WORK AND PAY YOUR OWN WAY!