Implications of unregistered and kinship marriages

What is important for parents to know when they want, as they say, "to arrange the happiness of their children"?

Marriage is the free expression of the will of a man and a woman. A marriage cannot be contracted without the free and full consent of those entering into marriage, even out of good intentions (Article 12 of the Family Code of the Republic of Tajikistan, Article 23 of the International Covenant on Civil and Political Rights).