first you need to settle your second sister.

this is very very very very old tricky condition for every family.

if one of you dont wanna sign = whole land cannot sell.

now another big issue is the land is joint name with Mr J which is an outsider, if anything happen to him and his wife/children dont wanna sell, then the land forever stuck there.

Gov don't know, but those children will attend the harta pusaka hearing to claim their part.