While ambling about your local cemetery, you stumble upon a grave marker situated before a six-grave plot. Glancing down, you notice an inscription upon the family stone. It reads:
Here lie…
2 Grandmothers with their 2 Granddaughters
2 Husbands with their 2 Wives
2 Fathers with their 2 Daughters
2 Mothers with their 2 Sons
2 Maidens with their 2 Mothers
2 Sisters with their 2 Brothers
Yet but 6 corpses all lie buried here. All born legitimate, from incest clear. How is this possible?
If two widows had each a son, and each widow married the son of the other and had a daughter by the marriage, all the relationships will be found to result.
Let’s say the first widow, W1, has a son, S1. The second widow, W2 has a son, S2.
W1 marries S2 and have a daughter D1. W2 marries S1 and have a daughter D2.
So we have:
2 Grandmothers (W1, W2) with their 2 Granddaughters (D2, D1)
2 Husbands (S1, S2) with their 2 Wives (W2, W1)
2 Fathers (S1, S2) with their 2 Daughters (D2, D1)
2 Mothers (W1,W2) with their 2 Sons (S1,S2)
2 Maidens (D1,D2) with their 2 Mothers (W1,W2)
2 Sisters (D1,D2) with their 2 (Half) Brothers (S1,S2)