Reproductive moral obligation in marriage is a religious philosophy about the responsibilities of community members to have children; not only to have children, but produce them in certain acceptable ways. In Catholicism, for example, many people believe this should happen only within marriage. According to the Principle of Procreative Beneficience, it is the only ethically sound way to "maximize expected value" of, not only the childrens' lives, but to the security and longevity of a future community, as well. It generally does not permit individual or even personal autonomy in marriage. Birth control is one such issue of debate in this arena. Sexual exploration between partners (those within the marriage only) is another area of controversy, as it reaches somewhat beyond traditional reproductive need as dictated by basic procreation principles -- couples who engage in sex for reasons other than procreation, for example.
Plato was one philosopher that talked about moral obligation centuries ago. This is relevant in terms of moral obligation in marriage because when people marry, they are legally bound by the laws of a state. Many of his arguments about morality and obligation appear in various forms these days. Social studies, politics, economics and the law all adhere to features of his similar doctrines. According to Plato's "Crito," you have both a political and moral obligation to abide by the law no matter what the circumstances; this includes marriage. The state theoretically creates you, then you have an obligation to behave in its best interest; anything you do contrary to that may ultimately lead your soul to ruin and to the ruin of your countrymen.
Legal philosophy of moral obligation in marriage expands on earlier Platonian moral philosophy somewhat; consequences of virtuous vs. non-virtuous behavior. Basically, when people break rules of a marriage, there are consequences. If you commit adultery, your husband or wife may cease any or all moral obligation in return. Problems often arise, however, due to issues of interpretation.
Moral philosophers often adhere to the idea of universality of moral obligation. There is also a level of reciprocity with moral obligation. While you are expected to behave in marriage, ways that are ethically sound (by not hurting, cheating or stealing), others are also expected to behave in a degree similarly toward you. Immanuel Kant was a moral philosopher who talked about moral rule, moral obligation, duty and conduct.