Addressing the question of whether a faithful spouse will be impeded in the hereafter by a faithless (or at least less faithful) spouse, Joseph Fielding Smith wrote:
If a man and his wife are saved in separate kingdoms, for instance, the celestial and terrestrial, automatically the sealing is broken; it is broken because of the sins of one of the parties. No one can be deprived of exaltation who remains faithful. In other words, an undeserving husband cannot prevent a faithful wife from an exaltation and vice versa. (Joseph Fielding Smith, “Celestial Marriage” in Blaine R. Porter, ed. The Latter-day Saint Family: A Book of Selected Reading [Provo, Utah: Brigham Young University Printing Service, 1966], 208-23, here, p. 214, emphasis added)
