Gray et al. propose that Human paternal behavior is best viewed as a triadic (mother-father-child) rather than a dyadic phenomenon (p. 2). Lawson & Mace add the additional element of multiple children, and suggest that the success of offspring is also affected by family size (number of other siblings). Putting these together, explain how having fewer children could actually promote reproductive success for fathers. 
Only use there two article as references to write!