How many brothers does Lady Farnese have?
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: