The following passage from a Boyd K. Packer talk, is one I'm quite familiar with. It has brought my parents, and thousands of other parents, comfort and a perception of control over their children's salvation.
It is not uncommon for responsible parents to lose one of their children, for a time, to influences over which they have no control. They agonize over rebellious sons or daughters. They are puzzled over why they are so helpless when they have tried so hard to do what they should.
It is my conviction that those wicked influences one day will be overruled.
“The Prophet Joseph Smith declared—and he never taught a more comforting doctrine—that the eternal sealings of faithful parents and the divine promises made to them for valiant service in the Cause of Truth, would save not only themselves, but likewise their posterity. Though some of the sheep may wander, the eye of the Shepherd is upon them, and sooner or later they will feel the tentacles of Divine Providence reaching out after them and drawing them back to the fold. Either in this life or the life to come, they will return. They will have to pay their debt to justice; they will suffer for their sins; and may tread a thorny path; but if it leads them at last, like the penitent Prodigal, to a loving and forgiving father’s heart and home, the painful experience will not have been in vain. Pray for your careless and disobedient children; hold on to them with your faith. Hope on, trust on, till you see the salvation of God.” (Orson F. Whitney, in Conference Report, Apr. 1929, p. 110.)
We cannot overemphasize the value of temple marriage, the binding ties of the sealing ordinance, and the standards of worthiness required of them. When parents keep the covenants they have made at the altar of the temple, their children will be forever bound to them. President Brigham Young said:
“Let the father and mother, who are members of this Church and Kingdom, take a righteous course, and strive with all their might never to do a wrong, but to do good all their lives; if they have one child or one hundred children, if they conduct themselves towards them as they should, binding them to the Lord by their faith and prayers, I care not where those children go, they are bound up to their parents by an everlasting tie, and no power of earth or hell can separate them from their parents in eternity; they will return again to the fountain from whence they sprang.” (Joseph Fielding Smith, Doctrines of Salvation, comp. Bruce R. McConkie, 3 vols., 2:90–91.)
Packer goes on to discuss repentance, but it is un-mistakable, in this doctrine, that there is a path to heaven for wayward children ... a path that will ensure both parents and child live together in the after-life.
But, with the newest Latter-day prophet, has this doctrine been reversed? Russell M. Nelson said, yesterday, April 7, 2019:
The anguish of my heart is that many people whom I love, whom I admire and respect, decline his invitation. They ignore the pleadings of Jesus Christ when he beckons, “Come, follow me.” I understand why God weeps; I also weep for such friends and relatives. They’re wonderful men and women, devoted to their family and civic responsibilities. They give generously of their time, energy, and resources – and the world is better for their efforts. But they have chosen not to make covenants with God. They have not received the ordinances that will exalt them with their families and bind them together forever.
How I wish I could visit with them and invite them to seriously consider the enabling laws of the lord. I’ve wondered what I could possibly say so that they would feel how much the savior loves them, and know how much I love them, and come to recognize how covenant-keeping women and men can receive a fullness of joy.
They need to understand that while there is a place for them hereafter, with wonderful men and women who also chose not to make covenants with God, that is not the place where families will be reunited and be given the privilege to live and progress forever. That is not the kingdom where they will experience the fullness of joy, of never-ending progression and happiness. Those consummate blessings can come only by living in an exalted celestial realm, with God our eternal father, his son Jesus Christ, and our wonderful, worthy, and qualified family members.
The above passage seems to be talking only of people who never are baptized Mormon. But the last part of the above paragraph, and later in his talk, he makes it clear that he is including those "who have distanced [themselves] from the church" which would include prodigal children.
My belief is that God and Justice and Mercy are perfectly aligned; and that the only thing we truly have control over is how well we live the first and second great commandments. If we truly obey those commandments through our life, then we can stand fully prepared before the judgement bar of God.
I simply cannot believe that God would deny people like Mother Teresa and many other great people, entrance into heaven over a technicality such as baptism and temple work. If God is all-powerful and controls the judgement bar; and given the Mormon doctrine of proxy ordinance work, it seems very reasonable God could ensure a technicality were met in order to allow a person entrance into heaven, thereby allowing mercy her space, while ensuring men and women are granted the opportunity to learn through works (justice), which is what is most important in life.