In these cases of 'antenuptial fornication', it was the mother of the child who would be summoned first, they would be sternly rebuked and persuaded to name the father of the child if he was not an obvious boyfriend.
Not quite.
I don't know who produced that index listing, but whoever it was was absolutely wrong to list it as 'index of Antenuptial Relationships' because many if not most of the relationships listed are not antenuptial; antenuptial specifically means '
before marriage', not 'outside marriage' or 'out of wedlock', and there is no shortage in the Kirk Session records of relationships between couples who never married one another at all.
'Antenuptial fornication' means 'fornication before the marriage' so by definition anyone summoned for that sin was actually married. They had anticipated the wedding ceremony, and that generally became apparent when the first child was on its way after a rather indecorously short interval thereafter. In the case of antenuptial fornication the couple, by now married, were usually summoned together and dealt with together. Occasionally it was only the husband who was summoned.
In the case of a couple who were still not married, you're perfectly correct. The unmarried woman would usually be summoned first and urged to name the father, and then they would take steps to summon the errant father and rebuke both parties at the same time. They didn't always succeed, of course, which is what makes reading the Kirk Session minutes so fascinating.
You can read the KS minutes on the Scotland's People web site; choose Virtual Volumes and then put in the name of the parish where the proceedings took place. Complicated cases might involve several appearances by one or both parties at different meetings of the KS.