Useless added member, should be a local variable.

You don't need the variable for the whole scope of the function, put it in the usage scope.

Also we don't use m_ prefix for local variables.

It's not a good practice to repeat a search (m_BaseActorString.find(L"{gender}")).

I'd write it like:

const std::wstring pattern = L"{phenotype}";
auto patternPos = baseActorString .find(pattern);
if (patternPos != std::wstring::npos)
    baseActorString.replace(patternPos, pattern.length(), cmpIdentity->GetPhenotype());

Also I think that the name may content more than one pattern, then this code won't work. So:

#include <boost/algorithm/string.hpp>
// ...
boost::replace_all(baseActorString , "{phenotype}", cmpIdentity->GetPhenotype());

Close enough :)

m_BaseActorString.replace(m_BaseActorString.find(L"{gender}"), 8, cmpIdentity->GetGender());

We should avoid a hardcoded string in many places and magic numbers.

What's the type ? We usually avoid auto not sure why @vladislavbelov suggested it there.

can't you replace "{phenotype}" by pattern ?

per @elexis suggestion that we ought not use boost here, I'd replace this with:

size_t pos = base.find(pattern, pos);
while (pos != std::string::npos) {
    base.replace(pos, pos + 11,  cmpIdentity->GetPhenotype());
    pos = base.find(pattern, pos + 11);
}

(needs some testing, but ought to work and be optimised enough)