Mmaagwe Molly le Rraagwe Molly: Firstborn Societal shame?

It is a norm in Botswana, atleast in the Kanye village, where I was born and nurtured for about 20 years, to call parents by their firstborn child. For example, in my parents case my mother, Gaontebale, is simply known as Mmaagwe Molly and my late father, Lekgoanyana, was simply called Rraagwe Molly, or the mother and father to Molly, their first born child, respectively.
At the same time, I have come to realise that a significant number of firstborns are explicitly excluded from this honour: cousins, friends, and relatives. Further investigations reveal that these firstborn children are in most cases not biological children of their mother’s husbands, or “stepfathers”. And I am told they were often potrayed as a burden to the husband. And perhaps manifested by the self-explanatory tag of “Letlaleanya”, or the one that arrives (to the ‘new husband’s) already breastfed. In other words, stepchild. In most cases, the hounour of the firstborn naming is relegated to the second born, the biological child to both parents. 
For me, with considerations of yesterday’s (and today’s) context: I believe we owe an apology to the disrespected, marginalised and victimised firstborns who have been burdened with their parents “load”, whatever the reasons for their separation. 
To the unrecognized firstborns: we see you, we honour you, and we will fight with you. Forgive us, please.