Babies and vaccines

Would you let your 9 month old (with all applicable vaccines) grow up around a newborn with anti-vax parents?

My wife's cousin will be giving birth next month at which point my wife and I will have a 9 month old. My wife and her cousin are close and have really bonded even over thier successive pregnancies. My wife's cousin really wants our LOs to grow up together, but our values are very different. We trust in medicine and doctors while my wife's cousin is very anti-modern medicine and will not be vaccinating her soon-to-be newborn at any point of its life. When our LO was born, we asked anyone who wanted to be around him in his first months to get Flu, COVID and DTaP vaccinations or otherwise stay away. My wife's cousin refused and has only recently met our LO.

Obviously, I am concerned about my LO bringing illnesses to his younger cousin who will not have any added protection, but I am also concerned about the inverse. In addition to the health aspect of the situation, my wife's family is really close; a couple relatives moved closer to us solely because LO was born. There is already pressure to have the LOs spend a lot of time together.

We are not sure what to do, so we would like other's perspective to tell us if we are being crazy or not.