Can we claim with insurance company for epilepsy ?

It all depends on what the policy covers and the policy exclusions. Someone in your HR dept should be able to tell you if you are covered or not. Nearly all health policies do not cover conditions which existed before you were insured. Some exclude certain conditions completely, maybe that's the case with your company policy. Epilepsy cannot be cured, but it can be controlled with drugs. Some children develop a mild form of epilepsy, Petty Mal, which usually they grow out of by puberty. My son had this. Nobody else in my family ever had this, so it probably wasn't genetic. I don't see how the insurance company are dismissing this as genetic, but in my experience all insurance companies will try to find reasons not to pay out. Keep at it, you may get a payout if you are persistent.