I have a few   

Restaurant I worked at had about ten waitstaff, including me. Three of us shared the same birthday.   

I was 26 the first time I tried weed. My coworker gave me cookies before telling me what it was. Same day and around the same time, my 22 year old cousin, Ryan, tried weed for the first time with his coworkers.   

The following is because of how small this island is, but still pretty weird, even for O'ahu   

When I was 15 I was in a group home called Hale Kipa. I had a roommate named Ben, then another named Keanu. Also where I met my first girlfriend, Tammy. I was then moved to another home called Catholic Charities. While there, I found out someone there knew Keanu from school and Ben from his neighborhood. Eventually I got a roommate named Matthew. Turns out his sister is my ex, Tammy, from Hale Kipa.   

While in Catholic Charities, I met someone at school named Branden. Turns out he was living in Hale Kipa, and probably using the bed that I used. He ended up running away. I later got a different roommate named Brian, who became my best friend. Turns out our grandparents live a few houses away from each other, and his younger brother, Jay, is best friends with my cousin Ryan (the one from the previous weed story), and his older brother is Branden, who ran from Hale Kipa.    

My cousin Ryan has a brother named Sean. Sean was best friends with his neighbor, Branden (not the same guy from Hale Kipa). Sean and Ryan ended up moving from the south side of the island to the far west side. Branden's family ended up moving to the same neighborhood, a few buildings away from him. Branden's family ended up moving back to another part of the south side, right up the street from me.