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He is from a steeped footballing background as he is the son of former League of Ireland player Derek O'Brien , younger brother of fellow Drogheda United player Mark O'Brien and nephew of former Republic of Ireland internationals Ray and Fran .
 Derek O'Brien, Drogheda United, Mark O'Brien, Republic of Ireland, Ray, Fran
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Derek O'Brien, Drogheda United, Mark O'Brien, Republic of Ireland, Ray, Fran