I also have an experience of a female relative, claiming to be
younger than her younger sister. The family claimed she was younger
and my mother believes this is because she never married. I know that the
custom persists to this day in Haredi circles in Israel, for younger
siblings not to marry until older siblings get married. Sometimes the
younger one seeks permission >from the older unmarried sibling to get
married.
Varda Epstein
yknow@netvision.net.il
Researching; YANOVSKY, JANOVSKY,SCHAEFER,KOPELMAN