In Heaven there will be one marriage, not many. That marriage will be what earthly marriage symbolized and pointed to, the marriage of Christ to his bride. So we will all be married—but to Christ. To have a lot of marriages in Heaven would be like still offering sacrifices after the Lamb of God came and offered the ultimate sacrifice. Our marriage to Him is the true Marriage, of which the best of earthly marriages was a symbol and shadow. Those who did not experience marriage or had only a poor marriage on earth will be delighted with their eternal bridegroom, who has already gone to prepare a place for them. One day all Heaven will attend the ultimate wedding, and we will be his bride (Read Rev. 19:7-9).
However, I do envision that people who have had important roles in each others’ lives will continue to be friends—and that would include a lot of people who've been married. If a woman was married to a man, he died and she married another man I think she could have a meaningful deep friendship in Heaven with both.
For further insight, see this article by John Piper on the topic of marriage in Heaven.
For more information on the subject of Heaven, see Randy Alcorn’s book Heaven.