mulier puisne (myoo-lee-<<schwa>>r pyoo-nee). [Law Latin] Hist. The younger lawful son,
usu. distinguished from the bastard eigné (“the elder bastard son”).
“The common law developed one exception to its harsh doctrine of bastardy. Where the eldest son was born out of wedlock (the bastard eigné) and the next son was born to the same parents after the marriage (the mulier puisné), and upon the ancestor’s death the bastard eigné entered as heir and remained in undisturbed possession until his own death, the bastard eigné was treated as if he had been legitimate with respect to the inheritance of that land. The reason given by Littleton was that a person who was legitimate by the Canon law could not be bastardised posthumously, when he no longer had the opportunity to contest the issue.” J.H. Baker, An Introduction to English Legal History 559 (3d ed. 1990).
[Blacks Law 8th]