연애 - love & romance
애인 - person who gains one's affection / her beau or his belle (Sweetheart)
연인 - person with whom an intimate relationship ("deep affection") is established/ her man or his lady (SO, significant other)
남친 - Boyfriend, in current usage.
여친 - Girlfriend, in current usage.
남사친 - Male friend
여사친- Female friend
What bothers me in this context is the possibility of mistranslation or changing the meaning. The English word "lover" today means a sexual partner outside the context of marriage†, so if the Korean word is simply a gender-neutral term for boyfriend and girlfriend, then translating it as "lover" is a mistranslation.
†The English word "lover" almost always refers to a sexual partner, which is already enough to make it a mistranslation if the Korean word does not mean that. Strictly speaking, the word "lover" doesn't specify whether the "love" is in the context of marriage or not, but because English speakers will always use "spouse" or "husband" or "wife" and not "lover" to refer to a sexual partner in the context of marriage, the result is that if someone says "lover", it can virtually only mean a sexual partner outside of marriage.
If the Korean word has the same implications, then I have no problem translating it as "lover."
If the Korean word is very broad, and can mean boyfriend/girlfriend or husband/wife (and maybe even adulterer) and may or may not imply an active sexual relationship, then if there isn't enough context to determine which specific English word is correct (if it's unclear in the Korean whether they're married or not or what the gender is), then I would probably translate it as "beloved".
Edit: I couldn't get it to format correctly using * instead of † because it would italicize the entire paragraph until "always" (I tried putting a space but that just turned it into a bullet point list), so I just decided to use †.