Well I think Erza all ready knows that jellal loves her.But,gray and natsu,to me, think of Erza like big sister.Remember when during the tower of heaven natsu 発言しました he looked up to her. So in a way natsu kind of 発言しました it. With gray I am not sure,but he feel some type of way. Gray had a weird reaction when Erza was bitten によって Crobra's snake.