I wasn't born in but when I left I felt the same way you do. I was in from age 9 to 20, probably the most important years for developing the ability to make friends. When I left I didn't know how to make friends so the loneliness was sometimes overwhelming. I became very shy and went into my shell, unable to see the various offers of friendship at first due to the unhealthy mistrust of "worldly" people that was enforced on me all those years. I always thought were some ulterior motive when instead they just wanted to hang out or include me in their lives.
Luckily I woke up due to a persistent acquaintance who once point blank asked me why I was such a snob. I was shocked & hurt she'd say that but I immediately understood where she was coming from. I wasn't a snob, I was still wearing that smug JW persona that looks down on worldly people as evil, debauched and imminent roadkill when the Big A came down the road, despite not believing in that anymore. I realized I was treating certain people that way - people who were a bit "out there", alternative and different. Good people. It's frightening how much damage the cult causes us.
Get out there and do things - group things, like casual adult sports teams, hobbies, running clubs, night courses at the community centre, book clubs, whatever. Anything that gets you amongst lots of people. A smile and a casual conversation can be sometimes all you need. Of course, there'll be people you won't like or won't like you, that's par for the course.
As far as finding your non-JW cousins - try Facebook. Enter their names and you might find them.