Brethren

What does Brethren mean in American Law?

The definition of Brethren in the law of the United States, as defined by the lexicographer Arthur Leff in his legal dictionary is:

An old form for the plural of brother, now used, if at all, only to refer to persons only symbolically brothers, e.g., the Justices of the Supreme Court; members of the Senate. In some wills “brethren” has been interpreted to include the testator”s sisters-presumably under the pressure of context or natural equity.