A child born after death of his father
A). Posthumous
B). Orphan
C). Bastard
D). Progenitor
Posthumous
One word substitute is Posthumous.
Posthumous: (of a child) born after the death of its father.
Orphan: a child whose parents are dead.
Bastard: a person born of parents not married to each other.
Progenitor: a person or thing from which a person, animal, or plant is descended or originates.