Callback Hell with nested Retrofit calls

PeopleRepository.kt

peopleRepository.loadPeopleAsync().enqueue(object: Callback<PeopleResponse> {
            override fun onFailure(call: Call<PeopleResponse>, t: Throwable) { }
            override fun onResponse(call: Call<PeopleResponse>, response: Response<PeopleResponse>) {
                if (response.isSuccessful) {
                    val result = response.body()?.results
                    result?.let { characters ->
                        characters.forEach { character ->
                            peopleRepository.loadPerson(character.url).enqueue(object: Callback<PersonResponse>{
                                override fun onFailure(call: Call<PersonResponse>, t: Throwable) {}
                                override fun onResponse(call: Call<PersonResponse>, response: Response<PersonResponse>) {
                                    if (response.isSuccessful) {
                                        val filmUrls = response.body()?.films
                                        filmUrls?.let {
                                            filmUrls.forEach { url ->
                                                peopleRepository.loadFilm(url).enqueue(object: Callback<FilmResponse>{
                                                    override fun onFailure(call: Call<FilmResponse>, t: Throwable) { }
                                                    override fun onResponse(call: Call<FilmResponse>, response: Response<FilmResponse>) {
                                                        if (response.isSuccessful){
                                                            val film = response.body()
                                                            film?.let { filmList.add(film) }
                                                        } else {
                                                            errorMessageLiveData.postValue(R.string.people_list_loading_error)
                                                        }
                                                    }
                                                })
                                            }
                                            filmListLiveData.postValue(filmList)
                                        }
                                    } else {
                                        errorMessageLiveData.postValue(R.string.people_list_loading_error)
                                    }
                                }
                            })
                        }
                    }
                } else {
                    errorMessageLiveData.postValue(R.string.people_list_loading_error)
                }
            }
        })