What should I do when my parents refuse my marriage even though I am twenty-eight years old?

Parents do not have the right to prevent their son from marrying, as this would cause him to miss out on worldly and religious benefits. The son can marry even if the parents do not approve, because there is no obedience to a creature in disobedience to the Creator, and there is no obedience to parents in matters that harm the child. After that, he should strive to please them by every legitimate means.