While I don't mind
Millicent and
Matilda for twins I dislike giving them the rhyming nns
Millie and
Tillie. Twins spend enough of their lives being thought of as a set instead of being thought of as individuals. Giving them rhyming nns makes it that much worse. I would never give twin siblings names any more similar than I would give singleton siblings.
I prefer
Millie to
Tillie.