Reference for Yevamot 73:10
ת"ר ראשון ראוי להיות כהן גדול ושני ממזר מספק רבי אליעזר בן יעקב אומר אין ממזר מספק
Our Rabbis taught: The first [child]<span class="x" onmousemove="('comment',' Born from the levirate marriage, and in respect of whom it is doubtful whether he is a nine-months child of the deceased or a seven-months one of the levir. ');"><sup>25</sup></span> is fit to be a High priest,<span class="x" onmousemove="('comment',' His legitimacy is beyond all doubt. If he is the son of the deceased brother he is legitimate, though the subsequent levirate marriage is a forbidden one; and if be is the son of the levir, the levirate marriage itself is a lawful union. ');"><sup>26</sup></span> and the second<span class="x" onmousemove="('comment',' Any child after the first, born from the levirate marriage. ');"><sup>27</sup></span>