Most object NPs are unmarked. When there are two animate NPs, one of them can be marked with a so-called obviative marker. This is only the case with animate NPs. The NP marked for obviative is the new or non-topic NP. It can be subject or object, but mostly object. Many such sentences have no obviative marker.
Source: Fleury 2007
Source: Fleury 2007
Source: Fleury 2007
Source: Laverdure and Allard 1983: 37