Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
According to Roman law it was made easier for the slave to obtain release from his master than for the son to obtain release from his father; the manumission of the former was permitted at an early period, and by simple forms; the release of the latter was only rendered possible at a much later date, and by very circuitous means. Indeed, if a master sold his slave and a father his son and the purchaser released both, the slave obtained his freedom, but the son by the release simply reverted into his father's power as before. Thus the inexorable consistency with which the Romans carried out their conception of the paternal and marital power converted it into a real right of property.
Closely, however, as the power of the master of the household over wife and child approximated to his proprietary power over slaves and cattle, the members of the family were nevertheless separated by a broad line of distinction, not merely in fact but in law, from the family property. The power of the house-master--even apart from the fact that it appeared in operation only within the house--was of a transient, and in some degree of a representative, character. Wife and child did not exist merely for the house-father's sake in the sense in which property exists only for the proprietor, or in which the subjects of an absolute state exist only for the king; they were the objects indeed of a legal right on his part, but they had at the same time capacities of right of their own; they were not things, but persons. Their rights were dormant in respect of exercise, simply because the unity of the household demanded that it should be governed by a single representative; but when the master of the household died, his sons at once came forward as its masters and now obtained on their own account over the women and children and property the rights hitherto exercised over these by the father. On the other hand the death of the master occasioned no change in the legal position of the slave.
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Reference address : https://www.ellopos.net/elpenor/rome/1-05-original-constitution-rome.asp?pg=6