http://revach.net/article.php?id=4643

Section: Parshas HaShavua   Category: Story
Parshas Masei: Rav Zemele Volozhin Show No Sympathy For The Boy Who Is Tricked Into Marrying An Older Girl
One of the Chashuvim of Vilna once came crying to Rav Zemeleh Volozhin that he married off his son to the wise and kind daughter of a prominent family of Vilna, but to his surprise after the Chasuna they found out that the girl was 10 years older than the boy!

Rav Zemeleh cut him off mid-sentence and answered him light heartedly.  At the end of Parshas Masei (36:10), the Torah mentions the names of the Bnos Tzelafchad in a different order than previous mentioned in Parshas Pinchos (27:1).  Rashi comments that previously they were mentioned in order of their wisdom, while here they were mentioned in the order of their age.  Why here did the Torah mention them by age?

Rav Zemeleh explained that the gemara Bava Basra (119) says that the youngest any of them married was at the age of 40.  Surely the Torah would not want to reveal their ages before they married so it listed them in order of their wisdom.  Only here when the Torah says that they married their cousins, does the Torah finally reveal their true ages.  Apparently the Torah felt that after their marriage, no one worried if anyone would find out how old they really were.  (Pninim Uparpara'os)