This comes from The Connecticut Nutmegger, Vol 20, Number 4, March 1988, which indicates it was originally from National Genealogical Society, Nov-Dec 1986.
A stumbling block to the correct interpretation of genealogical records is the fact that terms used to denote degrees of relationship sometimes had different meanings than they have today.
BROTHER – The term “brother,” in addition to its obvious meaning, could indicate any one of the following relationships by blood or marriage: (1) the husband of one’s sister, (2) the brother of one’s wife, (3) the husband of one’s sister-in-law, (4) a half-brother, or (5) a step-brother. Sometimes the term ‘brother’ did not indicate any relationship by blood or marriage but rather was used to refer to a brother in the church.
IN-LAWS – The terms ‘father-in-law,’ ‘mother-in-law,’ ‘son-in-law,’ and ‘daughter-in-law’ have always indicated a relationship by marriage rather than by blood. When you find these terms in early American records, they may have the same meanings we give them today, i.e., the father or mother of one’s spouse and the husband and wife of one’s child. But they may also have very different meanings. ‘Father-in-law’ and ‘mother-in-law’ may refer to a stepparent and ‘son-in-law’ and ‘daughter-in-law’ may refer to a stepchild. The terms ‘brother-in-law’ and ‘sister-in-law’ are more likely to have the same meanings we give them today.
SENIOR/JUNIOR – Prior to the nineteenth century it is not safe to assume that the use of the terms ‘Senior’ and ‘Junior’ refers to a father and son. The relationship could have been that of an uncle and nephew or of cousins. Before the use of middle names, it was not uncommon to have two or more men in a family with identical names. The older man was known as ‘Senior’ and the younger as ‘Junior’. A still younger person of the name might use ‘3d’ following his name. It is important for the researcher to keep in mind that a man known in his younger years as John Jones, Jr. may have been known as John Jones Sr. after the death of the older man.
COUSIN – The term ‘cousin’ was once used generally to indicate almost any degree of relationship by blood or marriage outside the immediate family. In early New England the term was sometimes used to refer to a nephew or niece.
NEPHEW – The term ‘nephew’ derives from the Latin “nepos,” meaning grandson. Occasionally an early will refers to the testator’s grandchildren, both males and females, as “newphews.” However, for the most part the term was used as it is today to mean the son of a brother or sister and, occasionally, the daughter of a brother or sister.
“NATURAL” SON – When the term ‘natural’ son is used the researcher should not jump to the conclusion that it denotes an illegitimate relationship. What it always indicates is a relationship by blood as distinguished from a relationship by marriage or adoption. In seventeenth century English wills, it was more common to refer to an illegitimate child as “my base son” or “my bastard son.”
“NOW” WIFE – Shen this term is used in a will, it is often assumed that the testator had a former wife. This may be true but is not necessarily so unless he refers to children by a first wife and children by his “present” or “now” wife. When the term is used without reference to children, it more usually means the testator is indicating that the bequest is intended only for his present wife and should not go to any subsequent wife he may have.
“ALIAS” – the use of two surnames, joined by the word ‘alias,’ in early Amerian records usually indicates an illegitimate birth and that the person has joined the surname of his reputed father to that of his mother. However, there were other reasons for the adoption of surnames. Sometimes when children inherited through their mother they used both the father’s and mother’s names. Sometimes the name of the natural father, who had died, was joined to that of a stepfather. In cases of adoption, the original name and the name of the adoptive parent were sometimes used together.