The cast of Friends in Season 1 were approximately these ages:

• Jennifer Aniston (Rachel Green): 25 years old, same as her character who was about 24-25 years old.
• Courteney Cox (Monica Geller): 30 years old, while her character Monica was around 24-26 years old.
• Lisa Kudrow (Phoebe Buffay): 31 years old, while Phoebe was about 27-28 years old.
• Matt LeBlanc (Joey Tribbiani): 26 years old, with Joey being about 25 years old.
• David Schwimmer (Ross Geller): 27 years old, with Ross about 26 years old.
• Matthew Perry (Chandler Bing): 25 years old, with Chandler about 26 years old.

The actors were close in age to their characters except for Courteney Cox who was older than Monica, and Lisa Kudrow who was older than Phoebe by a few years.