"The birth of the boy."
Translation:Η γέννηση του αγοριού.
Γέννα is accepted, as it has the exact same meaning with γέννηση (although, γέννα is mostly used to describe the proccess of the child's delivery, and not the actual birth. Still, one can be used instead of the other here.)
Γενιά means generation, and it's a different word. Be careful with the spelling :)