How old are Barbie and her sisters?

According to Dream House, Chelsea is confirmed to be 6 (in on of the episodes, it was her 6th birthday. Skipper is at least 16 because she can work at a job (also in Dream House). For Stacie, back in the 90s, she was 8-year-old. Now, she is about 10-11 years old (her appearance is so obvious). Stacie has younger twin cousins about 8-9 years old. I don't know about Barbie, they wouldn't reveal her age on Dream House.