From Longman Dictionary of Contemporary Englishbe two/five/ten etc years somebody’s juniorbe two/five/ten etc years somebody’s junior (also be somebody’s junior by two/five/ten etc years)YOUNG written to be two, five, ten etc years younger than someone She married a man seven years her junior. → junior
Examples from the Corpus
be two/five/ten etc years somebody’s junior• His wife's name was Sarah; she was five years his junior, and she predeceased him by ten months.• The 42-year-old princess married Commander Tim Laurence, who is five years her junior, just before Christmas. 