When the Tricous lived is completely open to interpretation. We only know they lived there before Rainelle, not that it was long ago. There's nothing to indicate a time period except their clothing, which is modern.
Olive was impregnated by Grim when she was an elder, so she is old enough to have been an elder for 20+ years and be in the same generation as Cornelia. Cornelia could have had Morty at 20 and Olive could have had Nervous at 60, explaining the 40 year age gap between them. Willow is Olive's younger sister and her ghost is an elder, so she probably had Ophelia later in life.
There's also nothing to say all the neighborhoods are synchronized, to say nothing of the age changing drugs and such that exist in their universe.
Re: They did not all live in the same time, did they?
Olive was impregnated by Grim when she was an elder, so she is old enough to have been an elder for 20+ years and be in the same generation as Cornelia. Cornelia could have had Morty at 20 and Olive could have had Nervous at 60, explaining the 40 year age gap between them. Willow is Olive's younger sister and her ghost is an elder, so she probably had Ophelia later in life.
There's also nothing to say all the neighborhoods are synchronized, to say nothing of the age changing drugs and such that exist in their universe.