Reference for Yevamot 36:10
אלא אשת אחיו שלא היה בעולמו לר"ש היכי משכחת לה בחד אחא ומית ונולד לו אח אי נמי בתרי ולא יבם ולא מית
occurred first and the marriage took place afterwards!<span class="x" onmousemove="('comment',' In which case the third brother's birth took place during the period when she was forbidden him as the 'wife of his brother who was not his contemporary. ');"><sup>41</sup></span> Consequently<span class="x" onmousemove="('comment',' Lit., 'but not?' ');"><sup>42</sup></span> it must have been required [in connection with the view] of R. Simeon; and the first [Mishnah] was taught in order to point out to you how far R. Simeon<span class="x" onmousemove="('comment',' Who permits marriage with the third brother even where his birth occurred prior to the widow's marriage. v. supra note 6. ');"><sup>43</sup></span> is prepared to go<span class="x" onmousemove="('comment',' Lit., 'the strength of R. Simeon'. ');"><sup>44</sup></span> while the last Mishnah was taught in order to show you how far the Rabbis<span class="x" onmousemove="('comment',' Who forbid the marriage even when the birth followed the marriage. Cf 'pro note 4. ');"><sup>45</sup></span>