So My Brother Just Found Out That He Has Oral

So my brother just found out that he has oral herpes (but has never had any symptoms-but tested positive during a blood test), according to him he got it from my daughter. My daughter is 9 and gave her uncle a kiss (okay several-she hasn't seen him in over a year). My daughter didn't have an active cold sore at the time. In fact, she knows not to kiss when she has an active sore. This incident was 7 months ago. He is a single guy, and I have a feeling it could have been from a number of other things/people. Now he says, I should warn people about my daughter, I'm a horrible parent, and he is no longer my sibling. My question is how can I tell if it is my daughter's fault, and am I required to tell people she has herpes even when she is symptom free?