significant other

kumppani One's romantic partner, regardless of marital status or gender.
2000 March 9, "http://news.google.com/newspapers?id=u_ZHAAAAIBAJ&sjid=-u0DAAAAIBAJ&pg=3173,3905600&dq=significant-other+ +significant-others&hl=en Couples Working Different Shifts, Union Poll Finds," Deseret News, p. D7 (retrieved 27 Oct 2013):

Almost half of working women who are married or live with a partner are seeing their significant other only in passing because the two work different shifts, an AFL-CIO poll found.

More than half (57 percent) of consumers think it would be wonderfully romantic if their significant other booked tickets for a surprise international trip.

Dr. Nogueira said it was always preferable to have coaches drawn from a school's staff because a coach "is a significant other" to a student.

As in the rest of the hospital, a family member or "significant other" such as a lover or close friend, is allowed to spend the night in a patient's room on a cot.

If your spouse, children or other significant others are still whining about all those holiday leftovers you made them eat, maybe it's time to spruce up your culinary skills.