Contracts of marriage like other contracts, require competent parties. The law as to the competency of the parties to a marriage contract differs in many respects from the law as to the competency of parties in ordinary contracts. Certain people who are able to make other contracts are prohibited from making a contract of marriage, while on the other hand, some persons may make a valid contract of marriage who would be unable to enter into a valid agreement on any other subject. The restrictions upon the capacity of persons to marry fall into two general classes: 1st, prohibitions against contracting marriage at all, and 2nd, prohibitions against contracting marriage with certain persons. The various classes of people who are prohibited from contracting marriage will be discussed in the following sections.