Or Bob lives in a society with no concept of bastardy.
Enforced: The work was written under the patronage of a medieval ruler who wanted to make it very clear that only those with legitimate Royal Blood have either the right or the character to rule over others.
Invoked: Maria has an affair with the king, hoping that his illegitimate son, Bob, will be his downfall.
Exploited: Bob's adoptive parent fosters his resentment toward his father the king.
Defied: ...But Bob refuses to be controlled by his past, and lives a normal life.
Discussed: Two characters wonder whether newborn bastard Bob will be a problem later on.
Conversed: Alice and Bob see a play about a Bastard Bastard, and critique it.