Reference for Kiddushin 158:14
אמר ריש לקיש
[IF HE SAID,] 'SHE DIED, AND THESE ARE HER CHILDREN: HE MUST BRING PROOF OF THE WOMAN AND OF THE CHILDREN. <big><b>GEMARA: </b></big>Rabbah son of R'Huna said: And in all cases it means that they cling to her.<span class="x" onmousemove="('comment',' The children are minors, who cling to this woman. Then her motherhood does not require proof.');"><sup>18</sup></span> Our Rabbis taught: [If a man declares,] 'I married a woman overseas, he must bring proof about the woman, but not about the children; he must bring proof about the adults, but not about the minors.<span class="x" onmousemove="('comment',' Who cling to her.');"><sup>19</sup></span> Now, when is this said? In the case of one wife. But in the case of two wives,<span class="x" onmousemove="('comment',' He affirms that he married two wives, of whom one died, while these are the children of the survivor.');"><sup>20</sup></span> he must bring proof about the woman and about the children whether adults or minors.<span class="x" onmousemove="('comment',' The clinging of the young children does not prove her parentage, since she may be their foster-mother.');"><sup>21</sup></span> Resh Lakish said: