Focal segmental glomerulosclerosis (FSGS) is a chronic scarring disease of the kidney. In the situation that you describe, I would be concerned about a genetic cause of the FSGS as both of your sons apparently have the disease. I assume that both of your sons have had kidney biopsies to confirm the disease. There are a number of familial (genetic) forms of FSGS and in some cases genetic testing is possible. Cyclosporine is one the drugs used to treat some forms of FSGS but it is unlikely to be very effective in the genetic form of the disease.
Treatment of genetic FSGS is very difficult and no treatment is recognized as uniformly successful. Use of ACE-inhibitors and ARB agents are commonly used in addition to drugs such as Cyclosporine, but prognosis is often very poor. I suggest that you discuss your concerns with your son’s nephrologist and ask for an explanation of the treatment regimen that is being offered.
You can learn more about FSGS on our web site at: https://www.kidney.org/atoz/content/focal