I'm sorry, Ada, but "After so much sigh and grief again and again, we finally understand that even a couple of lover, also need the time to come to temper " is just really bad English. The whole sentence is very poorly written, and the phrase 'come to temper' makes no sense at all. Nobody understands it because it has no meaning! It comes from a text on this site - http://www.englishbaby.com/forum/LifeTalk/thread/92277-best-time-your-life-meet. The text is by a Chinese person who cannot write English properly. Why are you reading this rubbish? You will never learn proper English if you waste your time on sentences written by people who have such a poor command of the English language. You have to avoid sites full of 'Chinglish' and concentrate instead on real English written by native speakers.

Maybe it's being used to describe the strengthening of their bond?

I've never heard the idiom. I can say with a great deal of certainty that it's not American. It also looks as if a non-native speaker wrote the sentence.

"Temper" can mean "balance" (both as a verb and a noun). Still, even reading the full sentence, it's a little strange. It looks like it's being used in a creative way, a bit poetic... or maybe what you've read it's just poorly written (that's my guess, because "a couple of lover" also has a mistake: it should be "a couple of lovers").

I've never heard it used before in America. However, temper can mean your mood. Someone with a bad temper is someone who easily gets mad. It can also refer to the hardness of metal.