A Player has asked about naming conventions in Brilight, and whether illegitimate children are surnamed differently from legitimate ones. Good question!
"Marriage" in Brilight is a complicated system of legal ties, not necessarily between only two people and not limited by the genders or races of people involved. (I.e., same gender marriage is fine and normal. Polyamorous arrangements are fine and normal. Some of those polyam arrangements are legally bound up as a "marriage"; others are not.) There are also cultural and religious entanglements which do not qualify as legal "marriage" but which are recognized by (some) of the populace as valid, but may face stigma from others.
A child is named, ultimately, by the person who bore it. But the person who bore the child can't just pick from the entire world of surnames; they have to have permission to use a surname. That permission can be implicit in the case of their OWN surname, or can be granted by signature from another on a legal document certifying parentage or guardianship of the child. So here are some examples:
Case A: Poor Mother, Rich Father
Hilda Poorson bears a child with Ergan Richars. The child could be surnamed "Poorson" because Hilda has the right to bequeath her surname to any child she bears. However, Hilda knows that her child will have more social capital if named "Richars". Ergan Richars signs a legal document agreeing to give the child his name, stating that he is the father and/or will assume a guardianship role for the child.
Case B: Rich Mother, Poor Father
Angelix Richars bears a child with Saule Poorson. The child can be surnamed "Richars" because Angelix has the right to bequeath her surname to any child she bears. Saule may or may not appreciate NOT having his name passed to his child, but that's for him to work out with Angelix; the law will only recognize Angelix's final word on what the child's name is, since she was the bearer. However, the child will NOT face social stigma having a mother's name rather than a father's; the taking of a mother's surname is an unremarkable and normal occurrence.
Case C: Polyamory Triad
Jasen Poorson bears a child with Bethar Middleclassers. Jasen and Bethar are in a polyamorous marriage with Twina Richars. Twina Richars can sign a legal document stating she assumes a guardianship role for the child and, in doing so, contributes her surname for Jasen to bequeath to the child he bore. The child is not genetically related to Twina Richars, but she is legally one of several guardians for the child.
Case D: Illegitimate Child
Fannye Poorson bears a child with an unknown father. No one is willing to step forward to assume a guardianship role for the child, so Fannye has no surname to give the child except her own. The taking of a mother's name is not stigmatized, but the surname itself may carry stigma with it--as, possibly, will the fact that the mother and child didn't have anyone "better" willing to step forward and grant their name.
Case E: Orphan
Sometimes a child of indeterminate birth is left on the orphanage doorstep. If no one is willing to step forward to assume a guardianship role for the child, their surname will be "Oarwen". This is rough elvish for "sea child". The polite fiction for these children is that their mothers were mermaids* who left the fin-less child with the land-dwellers.
* There are mermaids in this 'verse, probably.
** But that's not where orphans come from.
*** There is birth control and abortion, including magic options. The cantrip Prestidigitation works as spermicide and the Level 1 spell Chill Touch can abort a pregnancy. People who do not end a pregnancy either can't afford to or choose not to for personal, religious, or cultural reasons.
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Back to naming:
1. The child-bearer chooses their surname at birth.
2. Their right to use a surname comes either from (a) inheritance of their own or (b) permission granted from another person willing to bind themselves legally to the child.
"Marriage" in Brilight is a complicated system of legal ties, not necessarily between only two people and not limited by the genders or races of people involved. (I.e., same gender marriage is fine and normal. Polyamorous arrangements are fine and normal. Some of those polyam arrangements are legally bound up as a "marriage"; others are not.) There are also cultural and religious entanglements which do not qualify as legal "marriage" but which are recognized by (some) of the populace as valid, but may face stigma from others.
A child is named, ultimately, by the person who bore it. But the person who bore the child can't just pick from the entire world of surnames; they have to have permission to use a surname. That permission can be implicit in the case of their OWN surname, or can be granted by signature from another on a legal document certifying parentage or guardianship of the child. So here are some examples:
Case A: Poor Mother, Rich Father
Hilda Poorson bears a child with Ergan Richars. The child could be surnamed "Poorson" because Hilda has the right to bequeath her surname to any child she bears. However, Hilda knows that her child will have more social capital if named "Richars". Ergan Richars signs a legal document agreeing to give the child his name, stating that he is the father and/or will assume a guardianship role for the child.
Case B: Rich Mother, Poor Father
Angelix Richars bears a child with Saule Poorson. The child can be surnamed "Richars" because Angelix has the right to bequeath her surname to any child she bears. Saule may or may not appreciate NOT having his name passed to his child, but that's for him to work out with Angelix; the law will only recognize Angelix's final word on what the child's name is, since she was the bearer. However, the child will NOT face social stigma having a mother's name rather than a father's; the taking of a mother's surname is an unremarkable and normal occurrence.
Case C: Polyamory Triad
Jasen Poorson bears a child with Bethar Middleclassers. Jasen and Bethar are in a polyamorous marriage with Twina Richars. Twina Richars can sign a legal document stating she assumes a guardianship role for the child and, in doing so, contributes her surname for Jasen to bequeath to the child he bore. The child is not genetically related to Twina Richars, but she is legally one of several guardians for the child.
Case D: Illegitimate Child
Fannye Poorson bears a child with an unknown father. No one is willing to step forward to assume a guardianship role for the child, so Fannye has no surname to give the child except her own. The taking of a mother's name is not stigmatized, but the surname itself may carry stigma with it--as, possibly, will the fact that the mother and child didn't have anyone "better" willing to step forward and grant their name.
Case E: Orphan
Sometimes a child of indeterminate birth is left on the orphanage doorstep. If no one is willing to step forward to assume a guardianship role for the child, their surname will be "Oarwen". This is rough elvish for "sea child". The polite fiction for these children is that their mothers were mermaids* who left the fin-less child with the land-dwellers.
* There are mermaids in this 'verse, probably.
** But that's not where orphans come from.
*** There is birth control and abortion, including magic options. The cantrip Prestidigitation works as spermicide and the Level 1 spell Chill Touch can abort a pregnancy. People who do not end a pregnancy either can't afford to or choose not to for personal, religious, or cultural reasons.
---
Back to naming:
1. The child-bearer chooses their surname at birth.
2. Their right to use a surname comes either from (a) inheritance of their own or (b) permission granted from another person willing to bind themselves legally to the child.