Your half-sibling's grandchildren will be the half-first cousins once removed of your children, and vice versa. He passed away and a few years later she married his youngest brother and they had three children.
At a recent large family reunion, I met a young man whom I did not know. Your half-sibling's grandchildren will be the half-second cousins of your grandchildren, and vice versa. In such places genetic your relatedness coefficient with your in-laws and your step-relations is far from zero, since your relationship is through marriage and actual blood lines. Seniority matters as much as gene overlap!
The same pattern continues upwards for all earlier generations. It is also possible that the half you took has no overlap at all with the half your grandmother gave. I am honoured to share one sixty-fourth of your genes. It is possible that the half you took is exactly the same as the half your grandmother gave.
Fortunately, a bit of mathematical logic can clarify who should be called what, and why — and even measure the degree of genetic similarity between different relatives. And their children are your second-cousins:. Thus, first-cousins share two grandparents but no parentsand second-cousins share two great-grandparents but no grandparentsand so on.
In fact, if we regard siblings as 0-level cousins, then this reasoning applies to siblings too: children of 0-level cousins ie, siblings are themselves first-cousins.
In addition, there is lots of randomness in how genes are passed on each individual gets half of their genetic material from their mother and half from their father, but which bits come from which parent is chosen at random and cannot be predictedso we cannot draw precise conclusions with certainty. By contrast, your relatedness with yourself is one the largest possible value.
They finally decided that the words must be "maxi-mum" and "mini-mum". Of course, your genetic relatedness coefficient with your in-laws and your step-relations is zero, since your relationship is through marriage rather than actual blood lines.
Your children will be the half-first cousins of your half-sibling's children, and vice versa. Of course, the evolutionary imperative associated with relatedness coefficients does not tell the whole story. Your grandchildren will be the half-great-neices or half-great-nephews of your half-sibling, and your half-sibling will be their half-great-aunt or half-great-uncle. This attitude presumably has an evolutionary basis: our genes survived through the ages because our ancestors made efforts to help them survive by caring not only for themselves, but for their close relatives too.
Obviously that makes them my half-siblings.
You can about the intricacies of bee relationships in the appendix! Not a term used much in humans but quite common in pedigree livestock eg racehorses. She gave half of her genes to your mother, and then your mother gave half of her genes to you.
Your grandchildren will be the half-first cousins once removed of your half-sibling's children, and vice versa. Hey, My Dad has remarried and he and his wife my step mum are planning. Consider first the case of two half-siblings half-sisters or half-brothersthat is, people who share just one parent. For siblings, the situation is a little bit more complex. You will be the half-sibling of your half-sibling.
If you and your siblings each have children, then those children are first-cousins of each other. This approach averages out all of the randomness, while focusing on genetic similarities specifically due to family connections. So far so good:. If your ancestors really formed a perfect binary tree, you would have billions of ancestors at a time when humans existed at most in the millions, so all humans have multiple paths of descent.
For starters, if your parents have additional children besides you, then they are of course your siblings, that is your sisters and brothers:.
Meanwhile, a woman who marries your father after your mother becomes your step-mother or step-father, if the genders are reversed. Unlike with ancestors, there is no simple formula for your of descendants. My Kannada teacher told me about a group of women learning English, trying to figure out how to refer to your mother's older sister and your mother's younger sister: these are such different relationships to you that the single word 'aunt' could not possibly cover them both. Next consider your maternal grandmother.
Thus, children of first-cousins are second-cousins, and children of second-cousins are third-cousins, and so on. Then, if the two first-cousins each have children, then those children are second-cousins of each other; and their children are third-cousins, and so on:. They don't partition neatly into generations, either. After some discussion, we determined that my great-grandfather was the brother of his great-grandmother — making us third cousins. Other relatedness coefficients fall between these two extremes. Rather, you have to count up all of your children, and all of their children, and so on.
But on average, that is, in expectationexactly half of the genetic material you took from your mother originated from your maternal grandmother. For example, your maternal lineage is:. My great grandmother had six kids with my great grandfather. Your children will be the half-neices or half-nephews of your half-sibling, and your half-sibling will be their half-aunt or half-uncle.
When people have more than one child, this fattens the family tree, creating new relationships like sister and niece and great-aunt and more. Keeping track of family relations can be difficult. That perspective was nicely summarised by the early evolutionary biologist J. That is:. In an Indian village, your father's father's father's third wife might be your mother's sister or aunt, and their children share genes with you along both pathways -- and the language is rich with vocabulary to describe such possibilities.
What would be the proper term used to describe the different relationships here. You would hopefully protect your spouse over your second-cousin even though, strictly speaking, your relatedness coefficient with your spouse is zero since you have no actual blood relationship.
In a village with constant population of a few hundred, the cross branches have to be within living memory.
To see where your second-cousins come from, we have to move one more level up. Would your mothers new husband still be your uncle or your step dad? What about first-cousins-once-removed, and all of that? Siblings of your n th -level ancestors are your great Furthermore, the n th cousins of your m th -level ancestors, and also the m th -level descendants of your n th cousins, are your n th cousins m times removed.
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Very interesting - I've been working on a family tree, and though it is only 8 generations at its deepest, is wide and contains over 1, people, and I am now working on filling in these annoying voids, or attempting to link family fragments to mine who say they are related but I can't find the link, and make any corrections, etc. Different life forms can lead to different mathematics: eg, in many species of bees and ants the males have only half as much genetic information as females.
That is, three generations earlier, a brother-and-sister pair had married off with a sister-and-brother pair. For example, even if you have five children, it is possible that none of them will have children of their own, in which case your of grandchildren will be zero.
Jeffrey S. This article is very ethnocentric: going back to Toronto it might help, but not so much if you're headed to your ancestral village. Other family relationships can arise too. On the other hand, if they each have five children of their own, then you will have twenty-five grandchildren — a lot more.
I tracked the family tree down another generation but what I'm really curious about is what my grand-kids would be to my half-siblings kids? According to this definition, strangers have a relatedness of zero the smallest possible value. If your cousins have children, then what are they to you?
To deal with all of this, we as to each pair of individuals a relatedness coefficient which represents the expected fraction ie, the fraction on average of their genes which are forced to be identical by virtue of their family relationship. Thank you for the step-by-step explanation of relationships and how to calculate the coefficient of relatedness. This table can be thought of as indicating your level of evolutionary imperative to protect and assist your various relatives. Furthermore, my great-grandmother was the sister of his great-grandfather, too.
Add to this journey my recent DNA testing, which has brought some people potentially into my family. Family relations can lead to unexpected surprises. One special case is identical twinswho have identical genes and thus a relatedness coefficient of one.
You will be the half-aunt or half-uncle of your half-sibling's children, and they will be your half-neices or half-nephews. It was very helpful! In short, your ancestors form a perfect binary tree — simplicity itself. A friend in Bangalore told me a hobby of her mother's was to list all the possible ways to describe her kinship with her own husband.
To begin at the beginning well, your beginning, anywayyou surely had two parents, a mother and father:. Your half-sibling's grandchildren will be your half-great neices or half-great nephews, and you will be their half-great aunt or half-great uncle. Since each ancestor has two parents one mother and one fatheryou have a total of 2 n ancestors at level n : two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents, and so on.
If so can you calculate this for me? Well, first of all, about Furthermore, some people may share other genes with us just by chance; for example, if I meet a stranger whose eyes are brown just like mine are, that does not necessarily establish that we are close relatives. And, parents of adopted children should surely treat them just like biological children, despite the lack of true genetic connection.