Dear TS,
Try to sort out your feelings. What you're feeling may be familiarity due to affinity. There's a strong connection between related blood that you may find hard to pinpoint at the onset. It may be misconstrued as falling in love versus plain affinity.
My suggestion is not to fight the feeling. It's okay to be familiar and close to your cousin but always put things in the right perspective. You can take advantage of that relationship to where you have a cousin that you build trust on. Make friends with him, be close, create a healthy relationship. One that you can always be happy about without compromising it.
Remember to PUT THINGS IN THE RIGHT PERSPECTIVE!