The historical record indicates that queens were expected to bear heirs to secure the dynasty.

bear 在这里是动词，意思是"生育、生产"。这个词的本义是"承受、负担"，引申为"生育"的意思，特别用于指女性怀孕和分娩的过程。在历史语境中，bear heirs 特指王室女性生育王位继承人。