Question: Will there be marriage in Paradise?
ANSWER
Yes, there will be marriage in Paradise, but its exact nature is unknown because there will not be the nafs (a negative force within humans that prompts them to do evil) there. Islamic scholars state:

"Things in this world are a reflection, and an original source should exist for each reflection. A reflection is not formed if its original does not exist. The original, genuine forms of all worldly things exist in Paradise."

If one eats various fruit in one's dream, one will see when one wakes up that it was not real. Similarly, the inhabitants of Paradise will see the things in the world as something dreamt of, and they will attain the real ones. Worldly things are like the shadows and copies of their counterparts in Paradise. As a matter of fact, a hadith-i sharif says, "People are asleep. They will wake up upon dying." When we are transferred to the next world upon dying, worldly beings will be like those we see in our dreams. A hadith-i sharif says (what means):
(The similarity between the blessings in Paradise and those in the world is in name only.) [Bayhaqi]

It is stated that a person whose two days are the same is at loss. Accordingly, blessings will be increased each passing day in the afterworld. Every day, people will get different and much more pleasure from the same blessings. Moreover, they will be bestowed different bounties and different favors each day. No doubt should be harbored at all about Allahu ta'ala's power. Humans try to compare what they do not know to what they know, but something unknown cannot be compared to something known. It is declared in a hadith-i sharif:
(The world is like Paradise when compared to the womb and like a garbage dump when compared to Paradise.) [Ma'rifatnama]

Can Paradise ever be compared with a garbage dump? Just as it is impossible for a baby in the womb of its mother to know that it will be born and face various events, so it is impossible for a Believer who will go to Paradise to know the blessings he/she will attain there. A hadith-i sharif says (what means):
(In Paradise, there are blessings that are never heard and cannot even be imagined.) [Muslim]

Accordingly, the real form of marriage will exist in Paradise. Everybody will appear very beautiful to his/her spouse, and he/she will say that there is no one more beautiful or more handsome than his/her spouse. In Paradise, the delights of marriage, like all delights, will increase every day, and it will continue in this manner forever. The fact that there will be marriage in Paradise is established by Qur'anic verses and Prophetic sayings. When the blessings that will be granted to good people are described in the Qur'an al-karim, the following is said:

(Besides, We will wed them to houris having kohl-rimmed eyes [having beautiful eyes].) [Ad-Dukhan 54]

(We have created those with beautiful eyes anew for the ones whose books of records will be given from their right. We have made them virgins, devoted to their spouses, and of equal age.) [Al-Waqi'ah 35-38]

(In them are good-natured and beautiful-faced maidens.) [Ar-Rahman 70]

(For pious ones, there are gardens, vineyards, maidens with bud-like breasts and of equal age, and cups filled with drinks.) [An-Naba' 31-34]

(With them are large-eyed spouses who confine their lovely glances only to them. They are like pure white eggs that have not seen the light of day.) [As-Saffat 48-49]

In addition to them, it is stated in hadith-i sharifs:
(There is a difference of one degree between a martyr and a woman who obeys her Rabb, fulfills the rights of her husband, and who does not perpetrate a perfidy against him. If her husband is a Believer with good morals, he will be her husband. If her husband is not a suitable person, Allahu ta'ala will wed her to a martyr in Paradise.) [Tabarani]

(A martyr will be wedded to a houri in Paradise.) [Imam-i Ahmad]

(If one of the maidens of Paradise came to the world, the space between the earth and the sky would be filled with pleasant scent, and she would light up the space between these two.) [Bukhari, Muslim]

Those who die unmarried or in childhood, too, will get married in Paradise. Everyone will be of the same age.

Which one will she be with?
Question: In Paradise, will everyone not be with his/her spouse in the world? Secondly, what will be the situation of a woman who married twice? If she loves her first husband or her second husband more, will she not have the right to express a preference?
ANSWER
By and large, all people will be with their spouses if both of them are in Paradise. Our mother Umm-i Habiba asked our Master the Prophet whom a woman would marry in the next world if she married a second man after the death of her first husband and if she again married a third man after getting a divorce from her second husband. Our Master the Messenger of Allah replied, "Such a woman is free. In the next world, she will be with the one who had good morals. A person who has good morals attains the goodness of this world and the next." This means to say that she will be with the one whom she loves most. If she does not want any of them, she will not be with any of them, for there will be no sorrow in Paradise. Those who die unmarried or in childhood will get married in Paradise, too. And everyone will be of the same age.

What about unmarried people?
Question: Houris will be given to the people who will go to Paradise married after their death. What about unmarried ones?
ANSWER
Worldly marriages will end. That is, everybody will go there unmarried. If one is married in this world and one's spouse has died without faith, one's spouse will go to Hell and stay there eternally.

All the inhabitants of Paradise will be given houris and ghilman who will work in the service of them. There will be no unmarried person in Paradise.