The actor who played Young Ethan, Stan Kirsch, was almost 27 at the time this aired. Kirsch is actually a year older than Jennifer Aniston and Matthew Perry, both born in 1969.
Courteney Cox was actually 31 by the time this episode aired, whereas Monica is five years younger, at 26.
Monica says that she is 25 years and 13 months old. Given that this episode aired 4 May 1995, she was likely born early in April of 1969.