Definition and Theorem as siblings

[switzel]

This is related to #238

kaotheorems.sty automatically defines certain theorem styles where definitions and theorems are numbered independently:

        \declaretheorem[
                name=Theorem,
                refname={Theorem,Theorems},
                Refname={Theorem,Theorems},
                numberwithin=section,
        ]{theorem}
        \theoremstyle{kaodefinition}
        \declaretheorem[
                name=Definition,
                refname={Definition,Definitions},
                Refname={Definition,Definitions},
                numberwithin=section,
        ]{definition}

I would like them to be numbered by the same counter, as if definition was defined with sibling=theorem but I can't overwrite the definition of definition and I can't keep kaotheorems.sty from defining it. What is the best way to deal with this if want definitions to be called definition and not my_custom_definition?