Hi everyone,
This is my first post ever, but I couldn't resist the feeling to say something in this forum.
I find the scriptures and teaching of the church are really quite plain and simple on this doctrine, which is the Lord's way.
Let me start in the Bible:
Ecclesiastes 3:14
"I know that, whatsoever God doeth, it shall be for ever: nothing can be put to it, nor any thing taken from it: and God doeth it, that men should fear before him."
Matthew 16:19 (See also Matthew 18:18)
"And I will give unto thee the keys of the kingdom of heaven: and whatsoever thou shalt bind on earth shall be bound in heaven: and whatsoever thou shalt loose on earth shall be loosed in heaven."
These scriptures make it plain that God intends His works to last forever, including marriage. This discusses the Priesthood sealing power being given first to Peter to perform ordinances that are to be valid in the hereafter. Any talk about it being questionable whether eternal marriages sealed by the holy spirit of promise are of effect (monogomaous or polygymous) is to deny what the Lord has spoken.
Mark 10:2-9
"And the Pharisees came to him, and asked him, Is it lawful for a man to put away his wife? tempting him.
And he answered and said unto them, What did Moses command you?
And they said, Moses suffered to write a bill of divorcement, and to put her away.
And Jesus answered and said unto them, For the hardness of your heart he wrote you this precept.
But from the beginning of the creation God made them male and female.
For this cause shall a man leave his father and mother, and cleave to his wife;
And they twain shall be one flesh: so then they are no more twain, but one flesh.
What therefore God hath joined together, let not man put asunder."
These verses teach us that God did not intend for divorces to exist. Why then would He supposedly condone the mass divorce of His people in heaven who have multiple ETERNAL sealings, does God contradict himself?
Now that being said there is also doctrine to support that we won't be attaining additional marriages in the Celestial Kingdom either. We will keep the covenant relationships we enter into in mortality, but by the time of final judgment it is finished. We will not be stealing other people's spouses because they are eternally bound... and those that are single will be ministering angels and not getting married either.
Matt 22:
23 The same day came to him the Sadducees, which say that there is no resurrection, and asked him,
24 Saying, Master, Moses said, If a man die, having no children, his brother shall marry his wife, and raise up seed unto his brother.
25 Now there were with us seven brethren: and the first, when he had married a wife, deceased, and, having no issue, left his wife unto his brother:
26 Likewise the second also, and the third, unto the seventh.
27 And last of all the woman died also.
28 Therefore in the resurrection whose wife shall she be of the seven? for they all had her.
29 Jesus answered and said unto them, Ye do err, not knowing the scriptures, nor the power of God.
30 For in the resurrection they neither marry, nor are given in marriage, but are as the angels of God in heaven.
31 But as touching the resurrection of the dead, have ye not read that which was spoken unto you by God, saying,
32 I am the God of Abraham, and the God of Isaac, and the God of Jacob? God is not the God of the dead, but of the living.
33 And when the multitude heard this, they were astonished at his doctrine.
Some may see this passage of scripture as contradictory to my other points, or even disproving the doctrine of eternal marriage altogether. However, I see it in perfect keeping with the other teachings. Jesus does not say that marriage will not be of effect in heaven, but that it won't be taking place in heaven. Furthermore only those marriages authorized to be binding have a continuance in the next life, so all those who are not sealed for time and all eternity will be as the angels of heaven and will not enjoy the higher blessings of exaltation as promised to Abraham.
Therefore it seems clear to me that eternal companionships will exist in heaven. Some will be polygamous and some monogamous, but the state they are in after final judgment will be final and binding.