Odd info on Great Grandpa's birth record. What should I do with it from here?

[AlenskHerms19495]

I have posted this on other sites and was wondering what folks on Rootschat theories are.
My great grandfather's birth certificate has a very odd piece of info. His name was Robert Verhoogen and he was born June 20th, 1916 in New York to Flemish immigrants from Antwerp, Francis Verhoogen and Irma De Ryck. (Immigrated to the US 1912 and 1913) We have the birth and death info of Robert's older brother Thomas Verhoogen born April 18, 1914, in New York and died 26 July 1916 in Manhattan, New York. But Robert's birth certificate doesn't have one sibling listed on his birth certificate, He has two. It says "How many children previously born?" and it is answered as "Two" then it says "How many children now living in all?" and it is answered as "Three" I understand if that child was born prior to the immigration that they would not have a NY birth certificate and would not be on the NY birth index, but they must have died in NY. Is there any way there was a mistake on the birth certificate, or is there a chance Robert really did have another sibling? Any theories?

Edit: I have now attached photos I found of two children who I assume are the siblings, It is certainly not my great-grandpa and Thomas because Thomas died when my great-grandpa was one-month-old and one-month-olds can't stand/sit up like that.

[Magiccat1978]

I had a quick look for you and I can see Irma's Naturalization Petition and the only child listed on it is Robert, I found the family on the 1920 US Census and again Robert is the only child listed. I will keep looking 

Magiccat 

[Magiccat1978]

Hi

I've had a quick play around with the spelling of Verhoogen and I've found a Roman Catholic Baptism for a Antonine Mariam Richardum Verhoogan born 18 Apr 1914 at 306 W 23Rd ST, Manhatten, baptized 29 Apr 1914 at St Vincent de Paul. Parents shown as Francisco Verhoogan and Erma de Ryck.

It seems Thomas was a twin. I'll have a look and see if I can find out what happened to the baby.

Hope this helps,
magiccat

[AlenskHerms19495]

I looked back in the NY birth index for that year and there is no "Antoine" my guess would be that Antoine was Thomas baptism name.
Thank you so much for the info anyway

[Girl Guide]

I would be more inclined to think that Antonine is Anthony rather than Thomas.  Would not Thomas have been written as Tomas or similar?

Not an expert at latin versions of names so this is just a suggestion.

[AlenskHerms19495]

Antoine was a bit of a nickname for Thomas in the family,  Thomas had an uncle, and a great-grandpa both named Thomas and nicknamed "Antoine"
I have burial records for Thomas and I'll try scan and add it later.
Any theories/possibilities are appreciated.