No, what they told you isn't true. Perhaps they meant well—but it was insensitive and thoughtless of them to tell you this. Nowhere does the Bible say we won't be reunited with our loved ones in heaven, and in fact it teaches the opposite.
It is true that the institution of marriage was ordained by God only for this life, and not for heaven. The reason is because in heaven we will never die, and therefore marriage will no longer be necessary to carry on the human race. This is what Jesus meant when He said, "At the resurrection (when we are given new bodies) people will neither marry nor be given in marriage; they will be like the angels in heaven" (Matthew 22:30).
But this verse has nothing to do with the question of being reunited in heaven with our loved ones. After King David's infant son died, David knew that after his own death they would be reunited: "Now that he is dead, why should I fast (i.e. mourn)? ... I will go to him, but he will not return to me" (2 Samuel 12:23).
Thank God for His promises, and the hope we have of heaven if we know Christ. Thank God also that someday we will be reunited with those who have entered heaven before us. But most of all, thank God that in heaven we will be with Christ forever.