How many brothers does Lady Farnese have? It's mentioned earlier on that she was her father's only legitimate child, but then it's shown in chapter 252 that she has 3 more brothers, not including Serpico.

Could anyone clear that up, please?

Note: if it's explained beyond chapter 252, please explicitly mark it with a spoiler warning.
Farnese has 


  3 brothers and 1 half-brother.


In Vol. 14 Chapter 96,


   Serpico, his half-brother, was first introduced. His relation to Farnese, however, was only revealed on Vol. 22 Chapter 185.  


In Vol. 29 Chapter 251,


   Magnifico, his brother, was first shown arguing with their father, and he would later on join her and Guts' Travelling Party in their journey to Elfheim: 


In Vol. 29 Chapter 255,


  his other brothers, Giorgio and Poliziano, was first revealed, and this is the only appearance they have made so far: