is a name from Greek mythology. I'm not very familiar with the story other than she was Pyramus (sp?) were lovers of some sort.
Either way
Violet,
ELizabeth and Thisbe are an interesting group.
Elizabeth is common,
Violet not so much so and Thisbe is very uncommon. I think
Violet and Thisbe could work as sisters if the third child had a more unusual name like
Iona.