This is a verse from the Atharvaveda, which speaks about true love. Love which is pure and without any pre-conditions. What one has to keep in mind while reading this verse is that it was written during the period of the Iron Age more than 3000 years back.
The Universal language of love existed even then, the distinction between pure love and motivated or pre conditional love existed even in those ancient times.
Love is not between man and woman only, where sexual union is the core factor, but it can be between other individuals, without the incentive of sex. The Universal definition of love is much broader than what one sees with the sexual angle.
The union of hearts and minds
and freedom from hate I'll bring you.
Love one another as the cow
loves the calf that she has borne. ll
Let son be loyal to father
and of one mind with his mother.
Let wife speak to husband words
that are honey sweet and gentle. ll
Let not brother hate a brother,
nor a sister hate a sister,
unanimous, united in aims,
speak you words with friendliness. ll
I will make the prayer for that concord among men at home
by which Gods do not separate, nor ever hate one another ll
Be not parted - growing old, taking thought,
thriving together, moving under a common yoke,
come speaking sweetly to one another;
I'll make you have one aim and be of one mind. ll
Common be your water-store, common your share of food;
I bind you together to a common yoke,
United, gather around the sacrificial fire
like spokes around the nave of a wheel. ll
With your common desire I'll make you all
have one aim, be of one mind, following one leader,
like Gods who preserve their immortality.
Morn and eve may there always be a loving heart in you. ll
Hinduism's highest Sexual Union (prophet666.com)