Manusmriti
यवीयान्ज्येष्ठभार्यायां पुत्रमुत्पादयेद् यदि । समस्तत्र विभागः स्यादिति धर्मो व्यवस्थितः ॥ १२० ॥
If a younger brother begets a son on the wife of the elder, the division must then be made equally; this the law is settled.
english translation
yavIyAnjyeSThabhAryAyAM putramutpAdayed yadi । samastatra vibhAgaH syAditi dharmo vyavasthitaH ॥ 120 ॥
hk transliteration by Sanscript