Eldest
Defined in 4 dictionaries — Bouvier (1914), Black's (1910), Black's (1891), Anderson (1889)
Bouvier's Law Dictionary and Concise Encyclopedia
John Bouvier; revised by Francis Rawle · 1914
He or she who has the greatest age. The eldest son of a man is his first-born, the primo-genitus; L. R. 2 App. Cas. 698; I. R. 12 Ch. Div. 171. See Primogeniture.
Black's Law Dictionary
Henry Campbell Black, M.A. · 1910
A Dictionary of Law
Henry Campbell Black · 1891
He or she who has the greatest age. The “eldest son” is the first-born son. If there is only one son, he may still be described as the “eldest.” L.R.7 H. L. 644. Electa una via, non datur recursus ad alteram. He who has chosen one way cannot have recourse to another. 10 Toull. no. 170.
A Dictionary of Law
William C. Anderson · 1889
The eldest son is the first-born son — the primo-genitus. The words "shall become the eldest son " of a person living at the date of a will cannot, without an explanatory context, be extended beyond the life-time of that person; they are connected with the heirship of, and right of succession to, a living man."