What are options to lighten private areas? Ethnic skin

I suggest you see a skin care expert for treatment of this.  Although this is genetic and often has no "cure" you maybe able to get improvement.  Often this is from rubbing in the area as well and can be treated with local inner thigh liposuction.  Best, Dr. Emer.

Chronic moisture can cause skin irritation and result in hyperpigmentation of the inner thighs , posterior thighs and knees, underarms, buttocks and back. 
Before you spend $$ on peels or IPL, try these topicals.
This is called post-inflammatory hyperpigmentation (PIH). 
I recommend Melarase AM and Melarase PM creams from Kare Skin as well as a broad spectrum sunblock like Spectrase. Bothe are from Kare Skin. Scler-x post inflammatory hyperigmentation relief complex is a great supplement to take as well. See link below. 
Spectrase is a wide spectrum sunblock SPF 50+that is also recommended to prevent ongoing inflammation.