If I said it has to do with how you are related to different family members, your eyebrows might raise as you form an “oh” with your mouth and nod your understanding.
If you then asked me to explain third cousins twice removed, I would close my eyes (so you wouldn’t see them cross!), raise my brows, inhale impressively and say, “Hold on while I get my chart.”
Your consanguinity (kon-sang-gwin-i-tee)1 describes the kinship you have with another person who descends from an ancestor you both share. Merriam-Webster.com defines consanguinity as:
Kinship characterized by the sharing of common ancestors (derived from the Latin consanguineous, meaning “of common blood”). Kin are of two basic kinds: consanguineous (sharing common ancestors) and affinal (related by marriage).2
In determining consanguinity, be sure you use the most recent common ancestor when you begin the calculation. Otherwise, your result will be incorrect.
For example, in calculating my sister’s son’s relationship me, I would use my mother as the most recent common ancestor. First, I find my relationship to my mother (child) on the top row. Next, I find my sister’s son’s relationship to my mother (grandchild) in the left column. The point at which my column and his row intersect in the table reveals his relationship to me. Lo and behold, my sister’s son is my nephew.
However, if I made a mistake and used my grandmother as our most recent common ancestor, I would mistakenly conclude that my sister’s son is my first cousin once removed!
1. Dictionary.com app on iPhone, accessed 24 June 2014, “consanguinity.”
2. Merriam-Webster Online Dictionary (http://www.m-w.com : accessed 24 June 24, 2014), “consanguinity.”