In this article, we present an analysis of the complexity of grammatical constraints and their impact on early language acquisition of inflectional morphemes in Malayalam. We use the natural speech production data of two monolingual children acquiring Malayalam between the ages 1;9-2;10 and 2;3-3;0 and three bilingual children acquiring Malayalam-English between the ages 1;9-2;8, 2;0-3;0 and 1;10-2;11 to recover the underlying grammatical constraints that govern the correct productions as well as errors across monolingual and bilingual contexts. We find rules that reference lexico-semantic properties to be particularly challenging to young children.