This type of love does not seem to be mutual, and most people in a "loving couple" tend to discriminate against this, saying it is not a type of love at all. One-sided love commonly occurs when a relationship or marriage breaks, and one person moves on, while their spouse constantly thinks of them and attempts to win them back, often in vain.
See also: obsession
See also: infatuation
Consider: love triangle
John loves Jane. Jane loves John. Jane finds Jake. Jane now loves Jake. Jake loves Jane. John is sad, because he still loves Jane. John experiences one-sided love, even though Jane does not acknowledge that.