is US, how to apply Bama's GC?

I know I must file I 130 and have BaMa file I 485 for Bama's GC's. Here is a question: Do I have to file I 130 for Ba and Ma both? If I have I 130 for Mama, Can she file I 485 later to include Baba. Why to do this? Save 130 bucks on the I 130. Anyone knows a sure answer? I appreciate your experience and knowledge.