When defending marriage reality, people commonly use the term "a mother and a father" referring to what children need. The term unwittingly undermines the understanding of marriage reality. The Church teaches that a child has a human right to be born and raised in marriage because "it is through the secure and recognized relationship to his own parents that the child can discover his own identity and achieve his own proper human development."
Using “mother” and “father” preceded by the indefinite article ("a") obscures the uniqueness of the child and the irreplaceable relationship to his mother and father, and unwittingly accepts or supports several lies prevalent in the culture related to marriage and family. Here are some of the problems:
- It implies mothers and fathers are not specific to a child and therefore can be interchangeable.
- It expresses an idea (opinion) rather than a reality. Ideas are open to debate that leads to conflict, even if the ideal or ideal is supported by sociological research. Quality of parenting and outcomes for children are unrelated to the true meaning and purpose of marriage.
- It implies that complementarity defines marriage, but this is a red herring. Men and women do have complementary gifts that are important to child development, but complementarity is a consequence of marriage reality, not its purpose.
- It fails to emphasize that every child has his or her own mother and father, and that when one or both has been lost or they are not living in a state of unity through marriage, the child is in a state of privation.
Simply stated, in reality, marriage is the institution that unites children with their own mother and father. Do we need such an institution? Approached in this way, there is no need to defend complementarity of spouses. Both are understood in the description in a way that everyone knows is true. It also conforms to the universal desire of every person to know and be connected with their own mother and father, an experience of God’s plan.
Putting "a" before “mother” and “father” is so common that we are hardly aware when we use it. It is a difficult habit to break. But we must refuse to use the term as part of our witness to the Gospel of marriage.
 Donum Vitae II A1. Congregation for the Doctrine of the Faith. 1987 http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_...
 Note that sociological research on outcomes does not describe what marriage is or should be, but emphasizes the importance of men and women marrying before having children.
 In reality, marriage is the free choice of a man and woman to make themselves irreplaceable to each other, which is precisely what prepares them to receive a child as a gift from their own union. Expressing marriage in this way, communicates the reality in which complementarity is understood. It is not an objective of marriage.