Does a believer marry the Houris in the grave or after entering Paradise, and how can one reconcile the fact that a wife belongs to her last husband in this world with the idea that she belongs to the one with the best character among them?

The believer in his grave enjoys blessings and sees his place in Paradise, but the blessings of Paradise are not hastened for him in the Barzakh except for the martyr, due to what Al-Bara' ibn 'Azib (may Allah be pleased with him) narrated, that the Prophet (peace and blessings be upon him) said: "Then a door to Paradise and a door to Hell are opened for him. It is said: 'This would have been your abode if you had disobeyed Allah, but Allah has replaced it for you with this.' When he sees what is in Paradise, he says: 'My Lord, hasten the coming of the Hour so that I may return to my family and my wealth.' So it is said to him: 'Be at peace.'"

As for women in Paradise, some scholars have reconciled the two hadiths: "A woman will be with her last husband in Paradise" and "A woman will be with the best-mannered of her husbands." They explained each hadith as applying to a different situation. The first applies to a woman who died while still married to a husband; she will be with her last husband. The second applies to a woman who married several husbands and was divorced from all of them; she will choose the best-mannered among them on the Day of Resurrection.