The council bishops of 
Vatican II teaching here:
125. Marriage is likewise a friendship marked by passion, but a passion always directed to an ever more stable and intense union. This is because “marriage was not instituted solely for the procreation of children” but also that mutual love “might be properly expressed, that it should grow and mature”.(Gaudium et Spes 50) This unique friendship between a man and a woman acquires an all-encompassing character only within the conjugal union. Precisely as all-encompassing, this union is also exclusive, faithful and open to new life. It shares everything in constant mutual respect. The Second Vatican Council echoed this by stating that “such a love, bringing together the human and the divine, leads the partners to a free and mutual self-giving, experienced in tenderness and action, and permeating their entire lives”.(Gaudium et Spes 49)
Are human relationships exceptional or unique when compared to animals? The notion that the primary aim of marriage is procreation ignores higher human aspirations, not to mention simply biology. For the Christian, something higher is suggested by the marriage relationship, something that aspires to something more than the simple expression of sexual expression.
Remember that Amoris Laetitia is online here.
