The present work deals with the double challenge of considering childhood as a concept when apprehending it from a theoretical point of view and with its own historicity as a starting point, that is, taking into account a particular space and period of time. That being said, with Spanish 13th century as historical/space setting, and the notion of childhood —intimately linked to scarcity— that emerges from encyclopedialike texts from that time, we will focus our analysis in the initial scenes of the Libro de Alexandre —as per the critics, the book which gave birth to the Castilian clerical poetry, and for that reason extremely meaningful in relation to the heroism in its verses— which briefly unfolds the first childhood of the Macedonian hero.