[GAIUS libro libro secundo institutionum. ] §28.3.13.prPostumorum loco sunt et hi, qui in sui heredis loco succedendo quasi adgnascendo fiunt parentibus sui heredes.
[GAIUS, in the second book of the Institutes.] In the position of posthumous children are also those who, by succeeding to the position of a self-successor, become self-successors to their ascendants as if by a quasi-agnation.
ut ecce si filium et ex eo nepotem neptemue in potestate habeam, quia filius gradu praecedit, is solus iura sui heredis habet, quamuis nepos quoque et neptis ex eo in eadem potestate sint: sed si filius meus me uiuo morietur aut qualibet ratione exeat de potestate mea, incipit nepos neptisue in eius loco succedere et eo modo iura suorum heredum quasi adgnatione nanciscuntur.
For example, if I have in my power a son and a grandson or granddaughter born of him, because the son is prior in degree, he alone has the rights of a self-successor, although the grandson and granddaughter born of him are also in the same power. But if my son dies during my lifetime or leaves my power for any other reason, the grandson or granddaughter begins to succeed to his position, and in this manner they acquire the rights of self-successors as if by a quasi-agnation.
ne ergo eo modo rumpat mihi testamentum, sicut ipsum filium uel heredem instituere uel exheredare nominatim debeo, ne non iure faciam testamentum, ita et nepotem neptemue ex eo necesse est mihi uel heredem instituere uel exheredare, ne forte me uiuo filio mortuo succedendo in locum eius nepos neptisue quasi adgnatione rumpat testamentum: idque lege Iunia Uellea prouisum est.
Therefore, lest he should in this way revoke my testament, just as I must either appoint the son himself as heir or disinherit him by name, so that I may not make a testament unlawfully, so also it is necessary for me either to appoint as heir or to disinherit the grandson or granddaughter born of him, lest by chance, if the son dies while I am alive, the grandson or granddaughter, by succeeding to his position, should revoke the testament as if by a quasi-agnation; and this has been provided for by the Lex Junia Velleia.