<span class="searchmatch">sobrīnī</span> inflection of sobrīnus: nominative/vocative plural genitive singular...
initial so- must be an analogical renewal from soror. sobrīnus m (genitive <span class="searchmatch">sobrīnī</span>, feminine sobrīna); second declension sororal nephew nephew mother's sister's...
cousin's child 556-636 CE, Isidore of Seville, Etymologiae, page VIII: <span class="searchmatch">Sobrini</span> consobrinorum filii. (please add an English translation of this quotation)...