Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ămĭtīnus, a, um, adj. [amita], descended from a father’s sister; hence, ămĭtī-ni, ōrum, m., and ămĭtīnae, ārum, f., cousins, cousins-german, Dig. 38, 10, 1 and 10.