Margaret Poppy and
Eleanor Violet - two of my favorite flowers
As for siblings, I'd just go with my usual names I'd name children (
Alexandra,
Elizabeth,
William,
Charles,
James, etc.). If I were to carry on the theme with girls' middle names I might also use
Susan (as in Black-eyed
Susan), Bluebell,
Daisy, or
Glory (as in Morning
Glory). They're all flowers that have personal significance to me.