What firstborns are bad at If you have an older sibling, you may envy the fact that he or she came first, with whatever advantages that may confer. There is one area, though, where firstborns do seem to be disadvantaged. Researchers have theorized that firstborns are not as good at detecting biological kinship among strangers, because firstborns observed their own siblings directly in the care of the same mother right from birth, without having to discern resemblance. This was confirmed in a recent study, wherein researchers asked elementary-school students and adults, in both France and Taiwan, to pick out the pair of related people â€” including which newborns were related to which parents â€” from sets of photographs. In all demographic groups, firstborns performed worse.