"If you really love me, you'll sign this prenup."

"Prenups", as we call them in slang or vernacular, aren't necessarily a sign of wavering commitment by the love of your life.  Especially when the to-be-weds are getting hitched for a second (or, I suppose a third) time, are, say, middle-aged with grown children (or young ones), and assets. These situations are, well, complicated.  There's the delicate matter of explaining to your new bride-or-groom to be that you want to be sure the assets you already have go to your children.  Or that you want to make sure his / her assets, or community assets that the two of you hope to amass together, don't get targeted for, say, child or spousal support arrears, or an obligation to pay for college.

It helps if  the other person is thinking along the same lines. That way neither of you feels slighted when the other suggests making sure the children of each of you is protected.  Expect the other person to take it much more personally, though, if you are proposing a waiver of spousal support if y'all get divorced, or locking in as "separate property" - i.e. belong ONLY to one person - an asset that is going to go up, maybe dramatically, during the marriage - say, the business run by one of you. That's not to say is can't or shouldn't be done. 

Prenups don't have to be a romance killer.  Done well and handled delicately, they can make both of you less worried.