The custom of this borough is that the eldest son shall inherit those houses, lands, and tenements within the borough which his father held in fee simple at the time of his death, if he has not made or declared [orally] his will concerning the same. In such case that he has no sons, but daughters, then his daughters will be their father’s coheirs, saving to the wife the third part of the same, unless she has previously released her rights therein, or subsequently releases them.