How to claim share in grandfathers property from father

my age 30yrs unmarried. my grandpa have 3 sons & 45 acres land. 45 acres land given to 3 sons each one 15 acres my dad share 15 acres. my grandpa grandma expired. my dad & mom marriaged legal in 1980 with grandpa grandma permission. after 15yrs my dad got another marriage without permission of his parents and my mom. till then to now my dad living with 2nd wife not with my mom and me & no financial support. now I want that my grandpa given 15 acres land to my dad to me. that 15 land registered on my dad name. my dad not given land to me now. what can i do please give ur suggestions.