The mechanisms linking grandparental gender and involvement with grandchildren are probably more complex than previously understood. Grandmothers are likely to benefit from their central role as kin-keepers in their provision of care, while grandfathers in their older years benefit more from having a partner at their side. A basic argument here is that this indirect advantage for grandfathers dampens the general age-related reduction in their capacity for caring, making them better grandfathers than they otherwise would. Our reasoning rests primarily on normative explanations emphasizing the relevance of social roles and institutionalized expectations. However, rational choice theory represents an alternative theoretical strand that incorporates partly overlapping empirical implications. We provide a simple theoretical framework for exploring mechanisms behind grandmothers’ and grandfathers’ solicitude, and for assessing the credibility of the two main alternative arguments, while keeping an eye on evolutionary theory. We use data from the Survey of Health, Ageing and Retirement in Europe (SHARE), Release 2.3.0, waves 1 and 2. The empirical results are to a certain extent in line with predictions from normative explanations as well as rational choice theory. However, in regard to predicted consequences from living/not living with a partner, the main findings are consistent with the former but at odds with the latter. Having a partner in one’s older years increases individual capacity for involvement with grandchildren – most notably in the case of grandfathers. On a more general sociological level, the empirical pattern thus supports the idea that (older) men benefit more from the marriage institution or similar partnership arrangement than women do.