I have some loosely held thoughts on this.
To me, marriage seems synonymous with ownership. It serves the purpose to ensure there is no question of whose seed is produced; who reaps what they have sown. The children belong to the man who planted the seed. His wife belongs to him to plant in so there is no confusion. The man submits to the will of the father and works the thorny ground to bring his women into the same submission (Numbers 30). Because the seed can then be traced back directly through a man it always points back to the first Creator, the importance of the geneology. Utimately the only seed planted in all of us will be the Word, and we will bear fruit accordingly, as all other words/seed will be filtered out by their own wickedness.
When we are resurrected, we don't need to have the order of ownership in place because we will all be in submission to the Father, and only his word will endure.
Jesus was a recognizable male when he was resurrected and when he ascended into heaven. There is no fruit in endlessly dwelling on what bodies we will be ressurected in, but I think we can at least make an assumption that our bodies might be like his, since there were witnesses to a resurrected body.
If it is, then we might not be sexless beings. I don't see any reason why there would not still be sexual union between male and female in heaven. No marriage doesn't mean no sex, it just means no ownership.
Now as a man I have had a tendancy to make an idol of sex, so I don't want to propogate this idea just to hold on to something I like on earth, when there is really something better for us later. But I just want to point out that maybe "marriage" is an earthly necessity but sex is essentially just unity between a man and a woman.
Feel free to poke some holes in my line of thinking to help me grasp this better!