Kinship Relationships

Excerpted from University of California at Davis webpage:

http://entomology.ucdavis.edu/courses/hde19/lecture4.html

Table 1. Kinship relative to Ego among seven generations. Note that the children of the relatives in one entry are the entry one generation down and one collateral step to the right. For example, your grandfather's children (excepting your parents) are the entry to the lower right of grandfathers/grandmothers which are your uncles/aunts. And their children are your first cousins which is the entry to the lower right of uncles/aunts. Collaterals 2, 3 and 4 represent first, second and third cousins, respectively for the lineal kin in the same generation. For example, the second cousins twice removed in generation -2 for Ego are the second cousins of Ego's grandfather/grandmother.

COLLATERALS (Colineal and Ablineal) [description of terminology]

INTRODUCTION to KINSHIP

Kinship is really an extension of racial, genetical or ethnic groupings in that all of these can be further divided into relatedness categories such as tribes, clans or families. Individuals within family groups are typically organized around a central person (designate this person as 'Ego') in one-of-two ways:

Common progenitor (e.g. great grandfather)
Descendent (e.g. son, grandson)
The focus in both cases is on a person's genealogy (direct lineage for either descendents or progenitors) and not on the more complete case of their consanguinity (kinship). That is, everyone is part of:

Nuclear family--parents & children
Stem family--all direct ancestors & descendents
Extended family--nuclear and stem family plus assortment of other kin such as uncles/aunts, nephews/nieces & cousins.

Family of Man. Science writer Guy Murchie explains, "no human can be less closely related to any other human than approximately fiftieth cousin, and most of us are a lot closer. The main point about our universal interrelatedness is not that we are all descended from some common ancestors. Rather it is that each of us contains genetic contributions from practically everybody who ever lived. A single indirect genetic contact between Africa and Asia in a thousand years can make every African closer than fiftieth cousin to every Chinese. This can occur simply in consequence of the wanderings of nomads in intermediate territory. (from The Mountain of Names, Alex Shoumatoff, 1985).
Kin are divided into two general categories:

Lineal kin which are your direct descendents (children, grandchildren, etc.) and progenitors (parents, grandparents, etc.)

Collaterals which are all other kin. The collaterals can, in turn, be divided into two types:
Colineal--aunts/uncles, sibs, nephews/nieces. These are the siblings of lineal kin

Ablineal--cousins. These are the siblings of the colineal kin.

Cross-classification of Cousinships

by degree (e.g. first, second, etc.)
by generation removed (e.g. once removed, twice removed, etc.).

A person can only have one set of, say, first cousins in his or her own generation but may have two sets of first cousins once removed: i)your parent's first cousins are your first cousins once removed; and ii)your own first cousin's children are also your first cousins once removed. In the former case these first cousins are once removed back a generation and in the latter case they are once removed forward a generation.
the parents of your great grandmother or great grandfather are your second great grandparents and you are a second great grandson to them
the children of your grandnephews and grandnieces are your great grandnephews or great grandnieces and you are great grand uncles to them
your father's brother or sister is your uncle or aunt and you are a nephew or niece to them
the children of your first cousins are first cousins once removed and you are the same to them
the children of your second cousins are your second cousins once removed and you are the same to them
the grandchildren of your second cousins are your second cousins twice removed and you are the same to them
your grandfather's brothers are your great uncles, their children are your first cousins once removed and also your father's first cousins, and their grandchildren are your second cousins (or your second cousins are the children of your parent's first cousins).
An important aspect in understanding all kinship relations involves the biological pathways by which someone came to be your kin. This is especially true for all collaterals but is also important for lineal kin. For example, you have eight great grandparents representing four surnames (traditionally), three of which are not your own. That is, two of these three are associated with your mother's side and one of these three is associated with your father's mother's side. Thus in identifying grandparents it is important to keep the paths straight so that collaterals can be organized and traced accordingly. For example, your first cousins may be derived from either your father's side or your mother's side and your second cousins may be derived from four sources. These are the siblings of either: i)your paternal grandfather; ii)your paternal grandmother; iii)your maternal grandfather; and iv)your maternal grandmother.

Genealogy and Family History

Genealogy--history of descent of person or family from ancestor
Ancestry--evokes an image of a family tree branching further as it ascends
Lineage--stresses descent in line; single ancestor; Two people may have identical lineage but different ancestry
Pedigree--collective term referring to all consanguine relations
Vertical genealogy--concerned with lineal and colineal kin (e.g. grandparents; great aunts)
Horizontal genealogy--concerned with ablineal kin (e.g. second cousins once removed)
Note the various levels of information for genealogical research in Table 1. First level includes data sheets such as family group sheets. Second level are data summary sheets such as ancestral and lineage charts. Third level are personal and family biographies. One of the most useful references for researching your own family tree is the book by Eakle and Cerny (1984). In general, books on genealogy provide techniques and approaches for finding your remote kin. However they seldom provide broad overviews of kinship and pedigree relations. (Eakle, Arlene and Johni Cerny. 1984. The Source. A Guidebook of American Genealogy. Ancestry Publications Company, Salt Lake City, Utah).

Pedigree Collapse

If you kept multiplying your progenitors by two every generation--doubling your parents, their parents and so on--when you reached the time of Charlemagne (ca. 800 AD) you would have between four and seventeen billion of them. But obviously there were nowhere near that many people alive then or at any time. What prevents the theoretical population implosion from taking place is called "pedigree collapse". This is caused by cousins marrying cousins--the intentional mating between close cousins and random mating between distant ones who don't even know they are related. Each time cousins marry, duplication occurs in their descendant's pedigrees, because cousins already occupy a slot there. The farther back one traces any person's genealogy the greater the rate of duplication grows, until finally, when there is more cousin intermarriage than input from new people, the shape of one's pedigree stops expanding and begins to narrow. Each person's complete family tree, in other words, is shaped like a diamond. In the beginning it expands upward from him in an inverted triangle. At some point, hundreds of years back, the rate of expansion peaks, the base of the inverted triangle is reached and, overwhelmed by "collapse," the pedigree starts to narrow again, eventually coming to a point at a theoretical first couple--Adam and Eve. (from The Mountain of Names, Alex Shoumatoff, 1985).

Table 2. Consanguinity and equivalencies of genetical relatedness in genealogy.

CONSANGUINITY (Kinship)