Statistically Unlikely Events That Happened to Everyday People

I’ve always found the relationships in blended families to be pretty fascinating. This person has two half-siblings who are not even related to each other by blood in any way. But somehow, they’re both connected by their relationship to their common sibling, i.e., they’re related because one of each of their parents used to be married to the other.

Then add on top of that they are born on exactly the same day. These two people are sort of twins as far as their common sibling is concerned, but as far as they’re concerned, that doesn’t mean anything. I wonder if they meet at family gatherings, and if so, what do they think of each other?