Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ŭtĕrīnus, a, um, adj. [uterus], born of the same mother, uterine: fratres, Cod. Just. 5, 61, 21: soror, ib. 6, 59, 15; Cod. Th. 9, 42, 9, § 3; Vulg. Gen. 43, 29.