the queen’s firstborn sonfirstbornfirst‧born /ˈfɜːstbɔːn $ ˈfɜːrstbɔːrn/ noun [singular] 
her firstborn son
EXAMPLES FROM THE CORPUS
- Often, the firstborn are favoured from the moment of birth.
- They were expecting a son, brother to 2-year-old Hannah, their firstborn.
COLLOCATIONS FROM OTHER ENTRIES the queen’s firstborn son
your first child—firstborn adjective: the queen’s firstborn son her firstborn son