初しょ生せい

noun, noun which may take the genitive case particle 'no'

firstborn; newborn; first-produced

Refers to the first child born to a parent, a newborn infant, or the first product of something. Often used in formal or written contexts.

• 彼かれは初しょ生せいの子ことして大たい切せつに育そだてられた。