What counts as a biological individual? This question, which have been heavily debated among philosophers of biology, has crucial implications for our ontology of biology. Currently, the dominant view about this problem relies on two fundamental claims: (i) the category of biological individuals is more inclusive than the category of traditional organisms; (ii) biological individuals are evolutionary individuals. Taken together, these (logically independent) claims provide a unified framework for thinking about a variety of biological individuals in the living world. But recently, some philosophers have defended an alternative framework (Pradeu 2010, 2016; Godfrey-Smith 2013), where the notion of an organism and the notion of an evolutionary individual refer to two distinct and partially overlapping categories within the broader class of biological individuals. In this presentation, I will focus on the metaphysical interpretation(s) of this alternative view, by assuming a neo-aristotelician characterisation of the notion of a natural kind (Lowe 2009). Four (exclusive) metaphysical interpretations will be envisaged, namely: (1) both the categories of organisms and evolutionary individuals are natural kinds, (2) both correspond to mere accidental properties of biological individuals, (3-4) only one of the two is a natural kind but not the other. In the end, it will turns out that the most consistent of these four interpretations—from a metaphysical perspective—is the one which envisages the category of evolutionary individuals but not the category of organisms as a natural kind. This interpretation, however, supports several of the main aspects of the dominant view that is rejected by the abovementioned authors.