Responsa for Bava Batra 261:10
א"ל משום דקא מפיק לה בלשון ירתון
was] 'they shall take', or according to him who said [that the reading was], 'they shall inherit', [the question may be asked], surely one [has] not [the right] to give possession of something which is not yet in existence! And even R. Meir,<span class="x" onmousemove="('comment',' Lit., 'according to R. Meir'. ');"><sup>26</sup></span> who maintains [that] one may give possession of that which is not yet in existence, applies this law<span class="x" onmousemove="('comment',' Lit., 'these words'. ');"><sup>27</sup></span> [only to the case where the possession was given] to one who is [already] in existence,<span class="x" onmousemove="('comment',' At the time when possession was conferred. ');"><sup>28</sup></span>
Teshuvot Maharam
A. The term "sons" when used in vows does not include daughters. Moreover, a person who has sons has no right to give his daughter the status of an heir. Therefore, A's daughter is not entitled to the share of an heir in A's estate.
SOURCES: L. 236; Mord. B. B. 603; Agudah B. B. 190; cf. Sinai IV (1941) 10, no. 88.