One legend contends that Valentine was a priest who served during the third century in Rome. When Emperor Claudius II decided that single men made better soldiers than those with wives and families, he outlawed marriage for young men — his crop of potential soldiers. Valentine, realizing the injustice of the decree, defied Claudius and continued to perform marriages for young lovers in secret. When Valentine's actions were discovered, Claudius ordered that he be put to death.
Other stories suggest that Valentine may have been killed for attempting to help Christians escape harsh Roman prisons where they were often beaten and tortured. - See more at: http://variety.siam55.com/data/1/0066-1.html#sthash.5xeBEElR.dpuf