Mizuta Madaisuki

The Mizūta Twins are two identical twins who were part of the Rumbar Pirates. They were identified by Oda in a SBS question. A fan asked why one of the Rumbar Pirates that died singing had a sword in his skull. Oda explained that this was because they were two identical pirates who died two separate ways.

Mizūta Madaisukī (ミズータ・マダイスキー), the older of two, died by the sword during the last battle of the Rumbar Pirates. His name is a pun as mizutama daisuki means "I love dots". He admired Brook's fencing style and wanted to learn it from him.

Mizūta Mawaritosukī (ミズータ・マワリトスキー), the younger of two, died as he was singing Bink's Sake for Laboon, before succumbing to poison. His name is also a pun as mizutama waritosuki means "Dots ain't bad".

They both wear polka-dot shirt with blue dots. The older brother have more dots in his shirt than the younger have in his shirt.

Anime and Manga Differences
In the manga, the skeletal remains of the older of the two brothers had a sword piercing his skull along with others. In the anime, his remains has only swords sticking out of his body.