To create a lighting fixture that uses multiple light sources (such as a chandelier or a set of track lights), create a nested family.
The host family represents the hardware that supports the light sources (for example, the hardware for a chandelier, or the track for a set of track lights). Then you create another lighting fixture family that defines the light source (for example, the candles in a chandelier, or the can lights for a set of track lights). This family is nested into the host family.
A nested chandelier family
A nested track light family
The nested family (that defines the light sources) can be shared or not shared, depending on whether you want to be able to schedule the light sources and control their photometric parameters individually.