Ascendants and descendants in the direct line – father and daughter, grandfather and granddaughter, and so forth – may not marry each other.
Collaterals are prohibited from intermarrying if either of them is related to their common ancestor in the first degree of descent. Thus a man may not marry his sister, half-sister, niece or grand-niece. There is, on the other hand, no obstacle to marriage between cousins, including first cousins. As regards relations by marriage, a man may marry his deceased or divorced wife’s sister, aunt or niece; but he may not marry his former wife’s mother or her daughter by a previous husband.
The same rules apply as between a woman and her former husband’s relations. The laws have since changed and you may now marry your father in law or your mother in law may marry your spouse.
The law distinguishes between relations by blood (consanguinity) and relations by marriage (affinity). Blood relationship exists between persons descended from a common ancestor. Persons one of whom is descended from the other, such as father and son or grandmother and granddaughter, are related in the direct line. Persons who are descended from a common ancestor without being descended one from the other are related in the indirect line (collaterals). Father and son are related in the first degree direct, grandfather and grandson in the second degree direct, brothers and sisters in the second degree collateral (there is no first degree in the collateral line), and so on. The main consequence of relationship by blood is the duty of support.
Children in need, be they minors or majors, can claim support from their parents or grandparents. Destitute parents or grandparents can claim support from their children or grandchildren. In the collateral line the duty of support certainly does not extend further than brother and sister, and probably not even that far. In each case the claim depends on need and ability to pay. Relationship by affinity exists between a married person and the blood relations of his or her spouse – his father-in-law, mother-in-law, brother-in-law, and so forth. There is no duty of support between relations by marriage. Thus, a man is under no duty to provide support for his mother-in-law or his wife’s child by a previous marriage (stepson or stepdaughter). However, where the marriage is in community, he has to meet his wife’s obligation to support her mother or child by a previous marriage in his capacity as administrator of the joint estate.
Did you know that some Civil Marriages in South Africa have been indexed?
A Man may not marry his |
A Woman may not marry her |
|---|---|
| Grandmother | Grandfather |
| Mother | Father |
| Stepmother | Stepfather |
| Wife’s Mother | Husband’s Father |
| Daughter | Son |
| Wife’s Daughter | Husband’s Son |
| Son’s Wife | Daughter’s Husband |
| Sister | Brother |
| Wife’s Sister | Husband’s Brother |
| Brother’s Wife | Sister’s Husband |
| Son’s Daughter | Son’s Son |
| Grandfather’s Wife | Grandmother’s Husband |
| Daughter’s Daughter | Daughter’s Son |
| Son’s Son’s Wife | Son’s Daughter’s Husband |
| Daughter’s Son’s Wife | Daughter’s Daughter’s Husband |
| Wife’s Son’s Daughter | Husband’s Son’s Son |
| Wife’s Daughter’s Daughter | Husband’s Daughter’s Son |
| Brother’s Daughter | Brother’s Son |
| Sister’s Daughter | Sister’s Son |
| Brother’s Son’s Wife | Brother’s Daughter’s Husband |
| Sister’s Son’s Wife | Sister’s Daughter’s Husband |
| Wife’s Brother’s Daughter | Husband’s Brother’s Son |
| Wife’s Grandmother | Husband’s Grandfather |
| Wife’s Sister’s Daughter | Husband’s Sister’s Son |
| Father’s Sister | Father’s Brother |
| Mother’s Sister | Mother’s Brother |
| Father’s Brother’s Wife | Father’s Sister’s Husband |
| Mother’s Brother’s Wife | Mother’s Sister’s Husband |
| Wife’s Father’s Sister | Husband’s Father’s Brother |
| Wife’s Mother’s Sister | Husband’s Mother’s Brother |
A Man may not marry his |
A Woman may not marry her |
|---|---|
| Grandmother | Grandfather |
| Stepgrandmother | Stepgrandfather |
| Grandmother-in-Law | Grandfather-in-Law |
| Aunt | Uncle |
| Aunt-in-Law | Uncle-in-Law |
| Mother | Father |
| Stepmother | Stepfather |
| Mother-in-Law | Father-in-Law |
| Daughter | Son |
| Stepdaughter | Stepson |
| Daughter-in-Law | Son-in-Law |
| Sister | Brother |
| Sister-in-Law | Brother-in-Law |
| Granddaughter | Grandson |
| Granddaughter-in-Law | Grandson-in-Law |
| Stepgranddaughter | Stepgrandson |
| Niece | Nephew |
| Niece-in-Law | Nephew-in-Law |
