Pearl Krabs is the teenage whale daughter of Mr. Krabs. It is unknown how she could be Mr. Krabs' daughter since she's a whale. Though it could be possible that Mr. Krabs adopted her though that's unlikely since in medieval times Princess Pearl was a whale.
It could be that Mrs. Krabs, Mr. Krabs wife, was a whale. And it's also unknown what happened to Mrs. Krabs, she and Mr. Krabs may have divorced or she may had been deceased.
Pearl usually does not like it when Mr. Krabs is cheap, and gets really angry at him.
Pearl and one of her friends are known to have changed the word cool to coral, but when Mr. Krabs began to say coral Pearl called her friend Judy and told her the word coral was out.