This paper investigates factors influencing large family size and family realization of its benefits in Nanyala ward, Mbozi district, Tanzania. It is based on a household survey that involved 280 heads of households aged 50 years and above. Large family size is predominant in Nanyala ward. Factors influencing large family sizes include use of force by men, desire for security at old age, men’s desire to increase clan, high child mortality and parents believe that every child has his/her own luck. The paper reveals parents’ reflections on benefits and disadvantages of large family size. 63.2% of the respondents claim that life is so difficult that large family size is no longer beneficial. These parents indicated that if they were young, they would choose to have no child or not more than three children. On the other hand, parents revealed advantages of large family size as a source of farm labour, respect, bridewealth and health services. The study recommends various positive measures to be taken - such as reinforcement of population policies on marriage laws, education for women and improvement on health services, falsifying traditions and culture related to large family size.