Febrile seizures are caused by genetic changes in your child that make them more likely to have a seizure when they have a fever. This is called a genetic predisposition. This may seem obvious to you if there are others in your family who have had febrile seizures. But, often there is no family history of febrile seizures. This can be because the genetic predisposition is only in the child or the child has a combination of smaller genetic changes which they inherit independently from both parents. On their own, these genetic changes are not enough to cause a febrile seizure but when a child inherits a few of them then they have a predisposition to have seizures when they get a fever.