Are you Roger Clemens? 
(The former star MLB pitcher has four sons, all of whose names start with K; he chose that initial because it’s used in baseball scorekeeping to signify a strikeout.)
My father named three of us brothers with “R” first names. Brother #3 was JR, dad did not have a “R” name. I was a late in life surprise, so he reverted back to the “R” gimmick.
Growing up, there was a neighborhood family with E-Jay, R-Jay and D-Jay. All had middle names of Jay. Do not remember name of sister(s?).
I had remember seeing once in a file where they named their kids “Bambi” and “Thumper”. (And the girl was Bambi).
I read an trivia piece once where they listed many infamous men with the middle name Wayne.
Me either, unless it’s just generic Christian-ish names. Which are so common as to not really be a theme, and rather the default.
My mother was the seventh of eleven kids in her family, eight of them girls. During the middle of all the baby girls, my grandparents went on a “J” binge: Jean, June, Joan (my mom), and Judy.
One of my best friends in high school was from a big Catholic family; he was the youngest of nine kids. All of the children were named after Catholic saints, in alphabetical order, and as my friend was the “I,” he was named Ignatius. He went by “Nat.”
My cousins, whose surname begins with M, are named Maureen, Ann Marie, Molly, Michelle and Michael. No idea how that “A” snuck in there.
Years back, I worked with a woman who later had 2 sons (heard about the following thirdhand).
Her husband was, say, John James Smith.
Their first son was John Robert Smith.
Then the husband decided he really wanted a Junior… so the second son was John James Smith.
I gather this caused a LOT of confusion.
Me: I just call both my kids Sweetie. No need to remember names 
I have four cousins whose parents all gave them names which started with P.
I have another branch of my family, where there have been four generations with the same first name. But they’re not I, II, III, and IV because they all have different middle names.
I know a family who have three daughters, all of whom have Presidential surnames as their first names. Two of them are relatively common but one is a name I’ve never otherwise seen used as a girl’s name.
They are all names from the Bible.
Freakanomics. Many criminals with the middle name wayne or dewayne.
Boring. They should have gone with Adino, Calcol, Pelet, and Zibiah.
Polk? Or maybe Eisenhower?
I decided to not reveal any actual names in my post.
Plainly.
Personally, I think calling a little girl Ike is just mean.
That’s a theme? That’s the default for many people.
Bennett Cerf told a joke about a census taker visiting a German immigrant family. They had 13 kids, all girls, and all with names beginning with a ‘B’. Except the youngest, who was named Alice.
The census taker smiled at the mother. “Did you run out of ‘B’ names?”
No, she replied. "It’s just when my husband learned that the 13th was a girl, he exclaimed, 'Ach! Das is Alles!'" (German for ‘That is all!’)
I bet he was relieved when that fourth kid came along.
I just remembered another one. I have a colleague who, between her sister’s three kids and her own three kids, are all named after some video game franchise characters. IIRC, it’s a martial arts-type fighting game franchise, but I have no clue which one.
I wonder why Hilary Duff named her kids Townes and Banks.
Yes, it absolutely, positively, 100% is a theme. You don’t see it as one because, as I pointed out, our culture is submerged in it.