Recent Obit in A Newspaper wrote:My love for my Lord and my Heavenly Father allowed me to serve in Their eternal plan as an ordained Seventy, but I had not yet found my eternal companion until March, 197X. The daughter of [fiance's parents], [fiance] and I were engaged to be married in November 197X, however, [fiance] was called home to Our Lord on August XX, 197X and I believed my heart was forever broken, yet my faith and deep love for Christ gave me the trust that we would once again be reunited, and through His appointed prophet, President Spencer W. Kimball, I was granted the privilege of being married and sealed to [fiance] for time and all eternity on November XX, 197X.
I've not heard of this before, but a SP friend of mine (yes, an SP friend of SP) told me something about James E Faust allowing in the 1990s for the sealing of an engaged pioneer couple that the man died before they were married.
My hat is off to the LDS Church for doing this, both for the surviving fiance and the deceased's family members that are TBMs.