I can see the annoyance if you choose something truly unusual like Nefertiti Buttercup, but when they’re fighting over a name in the Top 10, grow up.
I think if as presented in the OP if it is a family member or a close friend and you come up with something creative like a really cool name or spelling like Nepis (Hittite for “sky”) or Madysen for Madison and they then take that for their own before your baby is born, yeah that’s BS and stealing your originality.
A boy I grew up with was given the same name as a 7-year older brother who had died at an early age of leukemia. Iirc, they were both named after a predeceased relative, per Jewish custom. I always wondered how the parents referred to each of them between themselves. Billy One and Billy Two? Our first Jimmy and our second Jimmy? It was so sad, I couldn’t reconcile it.
We were set on Ulysses if it was a boy, Ulysseia if it was a girl.
Then my brother and his wife ruined everything by naming their kid Achilles.
Haven’t spoken to them since.
Sounds like baby names are your family’s … weak point.
I had a Yorkie named Gracie.
According to my DIL I ruined the name for her to name her baby girls.
Too bad, I got there first. 
Sister produced the family’s first grandchild, a boy who was named Jake.
At the time Dad bred and trained working sheep dogs (kelpies). One of the prospects from latest litter had already been named Jake.
Now Dad had very low tolerance of any dog of his which didn’t work sheep proficiently and respond correctly to his commands. Jake the dog was well below average and normally would have had a low life expectancy or at best been sold off.
Jake the dog remained a happy and social dog who didn’t really give a stuff about working sheep or exhibit much intent of following instructions and yet, due to his fortuitous naming, lived the life of Reilly to a grand age.
So never took a “trip” to a quarry?
I’ve got a really common name for someone my age. Let’s say “John”.
My maternal great grandfather was John Smith. My grandfather was John Bob Smith and went by Bob. My uncle was John Luke Smith and went by Luke. Luke was the eldest of six children and the only boy. The Golden Child.
Luke has a child, but a girl. My parents had me and named me John after another John, not the family name.
Apparently this was absolutely wrong, wrong, wrong. How dare a girl use the sacred name.
A year later Uncle Luke had a boy, and named him John.
No one got us mixed up and AFAIK, this didn’t cause any permanent psychological trauma for anyone, but good god it was a sore point for years.
This is how it was in 1980:
So they don’t do the “Tony Uncle Al,” “Tony Uncle Johnny,” “Tony Uncle Philly” thing from The Sopranos where it’s the boy’s name followed by how the cousins refer to the boy’s father?
Lied to again by television.
Many, many, many years ago before I was married or even had any prospective spouse, I decided if I had a son, he would be named Matthew. Then, all of a sudden, there were little Matthews everywhere! How dare they!
When I finally was married and pregnant, my husband wanted to call a son Gideon, but we had a daughter and no more kids, so that name is still available. In middle school, my daughter had FIVE friends named Jessica, so I told her she could only have friends of that name, to make it easier on me. 
Sounds like reality is closer to Goodfellas:
“Paulie and his brothers had lots of sons and nephews. And almost all of them were named Peter or Paul. It was unbelievable. There must have been two dozen Peters and Pauls at the wedding. Plus, they were all married to girls named Marie. And they named all their daughters Marie. By the time I finished meeting everybody, I thought I was drunk.”
My brother has an unusual name, and he went through a fit of not liking it in preschool, or something, so we started calling him by an Anglicized short form of his Hebrew name, which was something like 15 or 20 on the list of popular names for the year he was born, and held steady for years-- it was probably way higher if you looked just at Jewish kids.
About 5 years after that, my mother went through this period of regret over ever giving him the other name.
Our last name is not terribly common, but it’s associated with the film industry, and anyone who goes into that industry is assumed to, well, have assumed the name, not come by it by luck. My brother now has this horribly common name, and a last name that might as well be "Hitchcock.’
Guess who is suddenly in love with the name on his birth ceritficate?
He contemplated changing it when he was 18, but couldn’t afford it. He was so glad he didn’t. Not his actual name, because I don’t have his permission, but his actual legal name that he uses in the film industry, and that he used to hate, is something very similar to Orion Hitchcock.
My mother picked the name partly because she didn’t want him to be Scott #4. But she wanted him to have a real name-- she didn’t want to name him Fugue, Cherrypicker, Cashew, or the sorts of things people used to attempt to be unique about 10 years ago. And she wanted him to have something you could turn into a Jewish name, however you had to do it.
Interestingly, the name did prove to be very unusual in my brother’s cohort-- but it just became popular about 5 years ago, so there are little boys running around with it.
Probably makes people suspicious that he isn’t using his real first name either.
I wonder how my mother would feel about the name becoming popular?
Regarding people naming their own kids the same thing-- there was a very observant Roman Catholic family down the street from us who had 5 or 6 daughters, all named Mary as a first name. But they were Mary Katharine, Mary Theresa, Mary Josephine, Mary Cecelia, etc. We called them Cat, Terrie, Josie, Cece, and so forth.
Same for Ashkenazi Jews. I would not have picked a name that a sister or cousin had given their child.
That being said, there are a lot of names out there
No, because now there’s a living Mahmoud, and you wouldn’t want to give your child his name. At least among Ashkenazi Jews.
Heck, we liked “Karl” as a name, but i worked with a guy named Karl, and it felt weird. So we picked something else.
Life is too short and too stressful to spend it getting upset and getting into feuds about names. Every person should have multiple names in mind for their future child as a precaution. I don’t plan on having children but I still have a list of over 20 unique names.
You know what’s a really cool spelling for a name? The way that everyone in the world spells it and expects it to be spelled. If you decide to name a kid with a “clever” spelling like Madysen, then any grief that comes from that in any way is entirely your fault.
My mother-in-law had a brother who had died when he was just a kid. According to my wife, her mother had wanted to name her son after her deceased brother, but didn’t because her brother and sister-in-law had already used it when their oldest son was born. I thought it was a little odd, as about the only times their families got together was a Thanksgiving, but there you go.
My next door neighbours are a blended family and they both have a couple of kids from previous marriages. There are two daughters called Abigail, 3 years apart.
They seem to cope ok with it, but it took me about 6 months to work it out. One of them would talk about Abigail, the other would chat about Abi. I thought they were talking about the same person.
Not sure if this fits in this thread but why not.
A family friend has a son named William and a daughter (so his sister) named Delores.
He is dating a woman named Delores who has a brother named William.