There is no universal law that suggests specific age gap between partners before they finally join in a blissful relationship. This subject, though often discussed has not yielded any conclusive theory that will tie the loose ends.
Traditionally a man is supposed to be older than a woman. In most cases, both sexes in the relationship have the same age. In rare instances, the woman is slightly older than the man. This phenomenon is wholly agreeable with the conventions of the society. It only becomes weird when one of the partners is far older than the other; say ten or fifteen years.
Age in relationships tend to be a great priority for many who are seeking to spend the rest of their lives with someone they truly love. Frustrations and regret sets in when the age difference is wide. This disparity may conflict with the individual goals and societal view of the relationship.