I want to sleep with my cousin.

Hello. Now I'm 30 and she's 29 or 28. When we were around 9 and 10 years old, she would sleep over because I'd tell my sister to invite her. My sister slept between us, but my cousin and I would hold hands and caress each other. One time I told my sister that my cousin likes me and she told her, saying that according to my cousin, she already knew because she saw it in my eyes. Another time, around 14, I wrote a letter to my cousin telling her I liked her. Never got a response. Since then, we've seen each other on average about two or three times a year. Now I have my wife and son. My wife and I tell each other everything and are very open-minded, and she knows my attraction to my cousin. My wife told me I have until our son turns one for trying to convince my cousin to get intimate with me. The baby is due in early December, so the period is almost over. My cousin and I have talked on WhatsApp, but it's not hot or frequent conversations. And that's where I ask for your support and advice. What can I do or say to make her feel like she wants something sexual with me? Even just once in a lifetime and already?? Help me! What do you advise? Thanks.