Cousins Explained

gg-child

g-uncle/g-aunt

first cousin once removed

second cousin

second cousin once removed

second cousin twice removed


ggg-child

gg-uncle/gg-aunt

first cousin twice removed

second cousin once removed

third cousin

third cousin once removed


gggg-child

ggg-uncle/ggg-aunt

first cousin thrice removed

second cousin twice removed

third cousin once removed

fourth cousin

The parents represent the common ancestors you have with your relative. Count down the row until you reach your generation. Now count down this column until you reach your relative's generation. This gives you your relationship to your relative. If you have only one common ancestor with your relative (perhaps this ancestor had multiple marriages), then the same chart applies but the relationships are half blood instead of full blood. 

In general, the person in the first row is the ***** of the person in the first column where ***** stands for the appropriate table entry, eg. sister, uncle, second cousin, etc. 

Example

Suppose I want to find out my relationship to the son of my grandmother's brother. Then the common ancestors that we share are my great-grandparents which are his grandparents. (I am assuming a full blood relationship). Therefore, reading from the chart we find that 

parents

child

g-child

ME

child

brother/sister

nephew/niece

g-nephew/g-niece

RELATIVE

uncle/aunt

first cousin

FIRST COUSIN ONCE REMOVED

I am the first cousin once removed of this relative!