You can find something of the true story of St Valentine, a priest who was martyred for his defence of the sacrament of matrimony,in Misyon, the online magazine I edit for the Columbans in the Philippines. You can find it here.
Below is the Opening Prayer from the Mass of St Valentine. You can find all the prayers and readings for his feast at http://carmelites.ie/Prayer/valentineliturgy.htm . Though the feast of St Valentine is no longer on its General Calendar – 14 February is now the feast of Sts Cyril and Methodius – the Church still venerates him as a martyr who defended the sanctity of marriage. He was truly a model diocesan priest.
OPENING PRAYER
All powerful, ever living God,
You gave St Valentine the courage to witness to the
Gospel of Christ,
even to the point of giving his life for it.
By his prayers help us to endure all suffering for love of you
and to seek you with all our hearts,
for you alone are the source of life.
Grant this through our Lord Jesus Christ, your Son . . .