While visiting various C of E churches and cathedrals in the UK, I have noticed there is usually (always?) a copy of the following table, printed, framed, and hanging on the wall somewhere in pubic view. I'll bet Henry VIII had something to do with it. (It also appears in the Book of Common Prayer, which is where I copied this from:)
A TABLE
OF
KINDRED AND AFFINITY,
WHEREIN WHOSOEVER ARE RELATED ARE FORBIDDEN IN
SCRIPTURE AND OUR LAWS TO MARRY TOGETHER.
A Man may not marry his
1 GRANDMOTHER,
2 Grandfather's Wife,
3 Wife's Grandmother.
4 Father's Sister,
5 Mother's Sister,
6 Father's Brother's Wife.
7 Mother's Brother's Wife,
8 Wife's Father's Sister,
9 Wife's Mother's Sister.
10 Mother,
11 Step-Mother,
12 Wife's Mother.
13 Daughter,
14 Wife's Daughter,
15 Son's Wife.
16 Sister,
17 Wife's Sister,
18 Brother's Wife.
19 Son's Daughter,
20 Daughter's Daughter,
21 Son's Son's Wife.
22 Daughter's' Son's Wife,
23 Wife's Son's Daughter,
24 Wife's Daughter's Daughter.
25 Brother's Daughter,
26 Sister's Daughter,
27 Brother's Son's Wife.
28 Sister's Son's Wife,
29 Wife's Brother's Daughter,
30 Wife's Sister's Daughter.
A Woman may not marry with her
1 GRANDFATHER,
2 Grandmother's Husband,
3 Husband's Grandfather.
4 Father's Brother,
5 Mother's Brother,
6 Father's Sister's Husband.
7 Mother's Sister's Husband,
8 Husband's Father's Brother,
9 Husband's Mother's Brother.
10 Father,
11 Step-Father,
12 Husband's Father.
13 Son,
14 Husband's Son,
15 Daughter's Husband.
16 Brother,
17 Husband's Brother,
18 Sister's Husband.
19 Son's Son,
20 Daughter's Son,
21 Son's Daughter's Husband.
22 Daughter's Daughter's Husband,
23 Husband's Son's Son,
24 Husband's Daughter's Son.
25 Brother's Son,
26 Sister's Son,
27 Brother's Daughter's Husband.
28 Sister's Daughter's Husband,
29 Husband's Brother's Son,
30 Husband's Sister's Son.