Don't confuse their (the possessive form of ‘they') and there (a pronoun and adverb). These two words sound exactly the same.
✗ In a democracy, people have the power to decide there own future.
✓ In a democracy, people have the power to decide their own future.
✗ Most women didn't work and were dependent on there husbands.
✓ Most women didn't work and were dependent on their husbands.