Do married couples need to live sexually? What is the Catholic interpretation of a married couple's need to be living sexually if they don't feel the need for it?
Let's say both of them don't feel the need to live romantically. They got to the point they are ok to live together like brother and sister. They love each other and they don't need sex. It's not an act of sacrifice or any kind of mortification, basically, they lost a desire to have sex and both are ok with it. They are both still fruitful though.

Are they still required to perform sex within marriage so they can keep procreating or this is accepted as ok by the Church's teaching?
The cessation of sexual acts between a married couple by common consent is seen as valid by the Church, particularly as they age. Also, the ancient interpretation (demonstrated by the Canons of the Councils of Carthage) is that upon raising a man to the diaconate (and, of old, presbyterate and episcopate) they must maintain perfect continence, that is, must cease sexual activity with their wives, if they have any.
That being said, the Catechism teaches:

The openness to fertility
1652 &quot;By its very nature the institution of marriage and married love is ordered to the procreation and education of the offspring and it is in them that it finds its crowning glory.&quot;Gaudium et Spes 48 #1; 50
Children are the supreme gift of marriage and contribute greatly to the good of the parents themselves. God himself said: &quot;It is not good that man should be alone,&quot; and &quot;from the beginning (he) made them male and female&quot;; wishing to associate them in a special way in his own creative work, God blessed man and woman with the words: &quot;Be fruitful and multiply.&quot; Hence, true married love and the whole structure of family life which results from it, without diminishment of the other ends of marriage, are directed to disposing the spouses to cooperate valiantly with the love of the Creator and Savior, who through them will increase and enrich his family from day to day.GS 50 #1; cf. Gen 2:18; Mt 19:4; Gen 1:28
1653 The fruitfulness of conjugal love extends to the fruits of the moral, spiritual, and supernatural life that parents hand on to their children by education. Parents are the principal and first educators of their children.Cf. Gravissimum Educationis 3 In this sense the fundamental task of marriage and family is to be at the service of life.Cf. Familiaris Consortio 28
1654 Spouses to whom God has not granted children can nevertheless have a conjugal life full of meaning, in both human and Christian terms. Their marriage can radiate a fruitfulness of charity, of hospitality, and of sacrifice.
1664 Unity, indissolubility, and openness to fertility are essential to marriage. Polygamy is incompatible with the unity of marriage; divorce separates what God has joined together; the refusal of fertility turns married life away from its &quot;supreme gift,&quot; the child (GS 50 # 1).

In other words, though a couple need not have sexual relations constantly through their lives, they must make an honest effort, particularly in the beginning of their conjugal life, to open themselves to fertility and receive any children which the Creator has prepared for them. A Catholic who marries with no intention of ever having children does not marry validly, but once children have come or old age or the Diaconate have rendered unlikely or impossible their arrival, a couple may agree to end sexual relations without prejudice to their matrimony, provided they keep &quot;radiat[ing] a fruitfulness of charity, of hospitality, and of sacrifice.&quot;