I have a best friend who is a guy (Im a girl).We are real close but every so often I just know that we develop

crushes on each other.We never act on it (and never plan to).The thing is, I know we get jealous if the other mentions someone of the opposite .I kind of like having him as my friend and want him all to myself all the time, and he me.When we are together we really dont want other people around, we love each others company and love being together.Do you think it is natural for platonic friends to be so jealous? Does it mean anything?