Applying for PR status with your family is recommended to show solidarity, unity, and rootedness. It doesn’t matter if you are living with family or separately. For example, if your family is staying in your home country, then still you can file for their PR application so long as they hold a dependant pass.
However, if you are staying away from family for an impending separation (divorce) then you need to think carefully.
You also need to have a minimum salary to live with your entire family comfortably in Singapore. Therefore, if your monthly earnings are less than $4000, it makes sense to apply just for yourself.