firstborn, eldest child
El primogénito del rey es el heredero del trono.
The king's firstborn son is the heir to the throne.
La pareja llamó a su primogénito Mark.
The couple named their firstborn Mark.
El primogénito heredó toda la propiedad.
The firstborn son inherited the entire property.
Tom y Mary esperan tener su primogénito el próximo mes.
Tom and Mary are expecting their first child next month.