How old was Rama and Sita at the time of their marriage?
From translation of Valmiki Ramayanam
1.In Bala kanda when Dasaratha asks for Rama to fight the Rakshass , DAsaratha tells
“My lotus eyed Rama is less than sixteen years of age and I do not think that he has ability to fight with Rakshasas.” 20.2
2.n Ayodhya Kanda when Rama meets Kausalya to bid fare well she says
“Oh Rama after you have completed seventeen years after birth , I always longed for my sorrows to come to an end.” 20.45
These two clearly indicates that
a.Rama got married at age of 16
b.Rama lived one year in Ayodhya after his marriage
But when in sundara kanda Hanuman meets Sita and asks about her she says
“I enjoyed life for twelve years in the palace of Rama with all my wishes fulfilled and was enjoying all pleasures which are proper for human beings.” 33.18
it could be translated as I lived for twelve years before marriage and afterwards I lived very happily with Rama.
So it is clear Rama was 16 and Sita 12 at the time of marriage