The correct option is B Consanguinity
'Relationship by blood or birth' is Option C, Consanguinity. Option A, 'Parentage' means origin of one's parents. Option B, 'Affiliation' means connection with a political party or a large organization. Option D, 'Nepotism' is the act of using one's power or influence to get job or advantage to their family members. Thus, options A, B and C are incorrect and the correct word for the given phrase is Option C, Consanguinity.