This is a very stupid question, but as legal policies go, it reflects around them. So I'm not alone. If someone was named "Goo Gle" meaning their full name was "Google" could they have legal authority to obtain the name Google.com, as cases where if someone's name is in a name they could legally obtain it through ICANN policies. However, I do not speak for the instance of simply Google but other domains like Games, Facebook, etc. It is possible for people to be named such of a kind, but usually in the near future they will implent some sort of feature where if you was named after the name had been incorporated you are no longer obligated to obtain it. Some professional information please, thanks.
Legal authority? Sure if one can demonstrate their claim. But as to whether they will get it, it depends as lawyers would say. For instance, one got abcddottld in 2000 and put a parking page. After about a year, someone used abcd to sell bowling balls. Six months later, abcd files a trademark application for abcd for "country-wide" or "jurisdiction-wide" (only within that jurisdiction) notice for bowling balls. It was eventually approved after some time. Generally speaking, abcd likely isn't able to get the domain because they have to show the owner knew about their trademark before getting the domain. I don't know how they'll be able to do that unless, say, the domain owner really knew about it. But...let's try a twist. Six months after the trademark application was approved, abcddottld's parking page showed ads for competing bowling ball products. Now the mark holder has a book to throw at them. Oh, and what I described above has been tested. It's gone both ways as each case has similar yet somehow a different factor or so in their disputes. And this doesn't apply just to Google. Or whoever the actual party is. Note: what I described above isn't limited. Like I said, it depends.
It doesn't matter what your real name is, by itself, it has no trademark rights. A trademark must be used in commerce to establish rights. In fact, you can be prevented from starting a business using your real name if it infringes upon an existing mark - i.e. you are 70 years old and were born with the name Ronald McDonald. You could not open up a restaurant using your real name. Once a registered mark has gone past 5 years from publication, it is virtually impossible to challenge the other trademark holders rights. Unless the mark was granted based on fraud or you made a successful genericized argument (which wouldn't give you trademark rights anyway), their rights are generally considered "cast in stone". Just challenging a famous mark as you have suggested would take years and years in court and require millions of dollars in legal fees. If you lose against a registered mark, the judge could order you to pay treble the other sides legal fees.