Looking for diagnosis-married to my 1st cousin

Hi
I(26Yr) married to my 1st cousin(25Yr) and our parents also 1st cousins to each others(Inter-marriages). Female baby 1st born to us developed nephrotic syndrome (Focal Segmental Glomeral Disorder, FSGS on renal biopsy) at 1.5 yrs and died of ESRD(End Stage Renal disease) at 21 Month despite CAPD(Continuous Ambulatory Peritoneal Dialysis). Then God gave us son who also got Nephrotic syndrome at 5 month's age and left us at 7 Months via ESRD. There appears to be a genetic disease involved. I have consulted many doctors, but got no answers. My Qs are
1- This disease is from which side or do we have both?
2- How should we diagnose it?
3- How to proceed and which tests we should have?
4- Now its been two years that we been planing.Should we and when should
we try for our next baby
Please reply because we both are very stressed and living aimlessly without babies.