Unless otherwise stated, Toobworld Central believes that TV characters are the same age as the actors who are playing them. So in the Toobworld timeline, Maureen Robinson was 40 years old in 1997 when the Jupiter Two blasted off and became 'Lost In Space'. That means she was born in 1957 and so she was eight years old in 1965, thus making her two years younger than Sally Draper (and me).
Wrap your mind around that.
* Weiner has the opposite problem with the young actress playing Sally than the producers of 'Lost' had with the kid who played Walt. If 'Mad Men' keeps jumping the storyline ahead a year or so with each season, she's never going to be able to keep up in her own personal growth.