Related for Yevamot 37:20
עשה בה מאמר ואח"כ נולד אח או שנולד לו אח ואח"כ עשה בה מאמר ומת הראשונה יוצאה משום אשת אחיו שלא היה בעולמו ושניה חולצת ולא מתייבמת
and<span class="x" onmousemove="('comment',' As to the objection raised (supra 18b): Since they exempt in the second case, what need was there to mention the first which could have been inferred from it a minori ad majus? ');"><sup>53</sup></span> [a stronger case is given after a weaker] 'not only this<span class="x" onmousemove="('comment',' The case in the first Mishnah, the birth of the third brother before the marriage of the second, where the birth occurred while the widow was still under a prohibition to marry him. ');"><sup>54</sup></span> but also that'.<span class="x" onmousemove="('comment',' The case in the second Mishnah, where the birth of the third brother occurred when the widow was already permitted to him. ');"><sup>55</sup></span> It was taught in agreement with R. papa<span class="x" onmousemove="('comment',' That when the birth of the third brother occurred prior to the marriage of the second with the widow of the first, R. Simeon agrees with the Rabbis. ');"><sup>56</sup></span> and in contradiction to R. Oshaia: If one of two contemporary brothers died without Issue, and the second intended to address a ma 'amar to his deceased brother's wife but before he was able to do so a third brother was born and he himself died, the first widow is exempt<span class="x" onmousemove="('comment',' From marriage and halizah with the third brother. ');"><sup>57</sup></span> as 'the wife of the brother who was not his contemporary', and the second<span class="x" onmousemove="('comment',' The widow of the second brother. ');"><sup>58</sup></span> may either perform the <i>halizah</i> or be taken in levirate marriage. If, however, he<span class="x" onmousemove="('comment',' The second brother. ');"><sup>59</sup></span> addressed a ma'amar to the widow and subsequently a third brother was born, or if a third brother was born first and he<span class="x" onmousemove="('comment',' The second brother. ');"><sup>59</sup></span> addressed the ma'amar to the widow subsequently, and died, the first widow is exempt<span class="x" onmousemove="('comment',' From marriage and halizah with the third brother. ');"><sup>57</sup></span> as 'the wife of his brother who was not his contemporary' while the second<span class="x" onmousemove="('comment',' The widow of the second brother. ');"><sup>58</sup></span> must perform the <i>halizah</i>,<span class="x" onmousemove="('comment',' The ma'amar addressed to the first widow not having 'the same force as actual marriage to render the second brother's wife her rival to be exempt from halizah as well as from the levirate marriage with the third brother. ');"><sup>60</sup></span> though she may not be taken in levirate marriage.