We are not given the luxury of choosing the women we fall in love with.
--Martog (Deep Space Nine)
Originally, as the Greek god Eros he was a fundamental part of life - the amoral desire for all things to mix and mingle. He was described as "the most beautiful of all the immortal gods, who loosens the limbs and overcomes judgment and wise counsel in the breasts of gods and all humans." With this aspect, Eros was the strength and power of love rather than the more romantic, sensual pleasure - those were the aspects of Aphrodite.
As the Romans borrowed Greek Mythology, he became the son of Venus and was named Cupid. There, Love moved from an effect to a cause. It was Cupid that had the bow and arrows, not Eros. From a mature power, Love became a mischievous boy casting arrows of infatuation without concern for the feelings of those who were struck.
The image of a "blind boy-boy" as Shakespeare called him in Romeo and Juliet was added in medieval art to represent what appears to be a entirely random process of how we fall in love. Some attribute this image to the followers of Alexander Neckham who added blindness to the attributes of Cupid. One early example of this from the poem titled 'Der Walsche Gast' (from about 1215) where the line Love says: 'I am blind and I make blind'.