I think this is a very good question. This might be where proxy baptisms for the dead come into play. We need to remember that a LOT of temple work will be done during the millennium and the dead will have a chance to guide the living in that endeavor during that time. The Lord will make sure that all will have the opportunity, whether in this life or the next, to receive the ordinances and blessings of the Gospel. No one will be left out unless it is by their own choosing.

Without knowing what was going on in his heart and mind and why your son-in-law did what he did, none of us on this earth can judge him. Only our Father in Heaven can do so because only He knows the full truth. It could be that he had some type of mental break down or an illness that was long hidden. All we can do is trust that God will make all things right and that there are truly no tears in Heaven. My heart goes out to you and I hope that you are able to find peace and comfort somehow. I cannot even imagine how shattered your life must be right now. You have my deepest sympathies.

“Either in this life or the life to come, they WILL return.”

We just don’t know enough about eternity. What does it mean that they “will return”? Will we be exalted and they “only” saved? What does that mean? Nobody on this earth seems to know a lot about eternity, maybe even if God revealed more knowledge about it to us we would not be able to understand or bear it. But we have those questions, They come to our minds, And it can be quite frustrating to get answers like the quote from Elder Eyring “You are worrying about the wrong problem. You just live worthy of the
celestial kingdom, and the family arrangements will be more wonderful
than you can imagine.” If someone is told that his question is actually nothing he should worry about that doesn’t seem to be very helpful. It might even appear rude and impolite and turn the person away, We might feel like the captain who went to see the prophet to be healed of his disease and who was very upset when the prophet didn’t even come out to greet him, but instead just sent his servant to tell him what to do. it is our choice to listen and do or to not do – with the corresponding results. So let us be humble and diligent, even though we do not get all the answers to those things that trouble our hearts and minds.

And let us be diligent in enquiring of the Lord. For he sent us “the Comforter, which is the Holy Ghost, whom the Father will send in my name, he shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you.” John 14:26. Asking in faith we can and will get answers. The comforter WILL comfort us.

“Hope on,
trust on, till you see the salvation of God.”