Dutch idiosyncrasies

Julia turned seven today. Which brings me to the latest in what is turning into a very occasional series of posts on Dutch idiosyncrasies.
Today's is the habit of congratulating people on birthdays. Not the actual person celebrating a new year - they do that too, but I don't consider it unusual.
No, they congratulate more or less anybody who has ever met, glanced at or read about the person whose birthday it is. I swear, if we had a dog, our guests today (each and every one of whom I love to death) would have congratulated it.
This is how it goes: Guest A walks in gives Julia hug and congratulates her, then Guest A turns to Irmie and says "congratulations on Julia's birthday." I consider this just on the edge of not being odd because Irmie was pretty intricately involved in Julia's actual birthday seven years ago. The A turns to me kisses me three times (left cheek, right cheek, left cheek) and then says "congratulations on Julia's birthday." Then they turn to Esther: big hug, "congratulations on your sister's birthday." Then on to Oma and Opa (grandma and grandpa). Same thing: "Congratulations on your granddaughter's birthday."
By the end of the afternoon, I heard this (honest): "Congratulations on your sister-in-law's daughter's birthday."(!)