Board Thread:Manga Discussion/@comment-25819382-20170718215047/@comment-4896558-20170719003115

Eusstass wrote: She's a woman.

In chapter 350, it has been revealed that Halkenburg didn't get along with his mother and two sisters.

That is unless Tubeppa considers himself Male, or Togashi retconned that information.

Duazul (their mother) had 4 children --> Camilla, Tubeppa, Luzurus and Halkenburg.

It's pretty obvious Halkenburg and Luzurus are men, so that basically confirms Tubeppa is the second sister.