Congratulations!That is assuming that I understand that you had a new baby?
Now that some here have helped with the origins of the baby's grandfather (you father or your inlaw?) let me see if we can shed a bit of light on the family.
First a quick check in the Croatian on line phone book shows 67 listings in Zagreb county alone.The name is spelled with diacritical marks over the s / and over the c /.The name would sound like Garashich.
At Ancestry.com there are 0 tree entries, 13 Social Security death index entries and 23 listings in US phone books.
I don't know how serious you are in pursuing this interesting and worth while genealogy search, but there is much that can be found on the internet.Also I would suggest that you look for marriage, birth, baptismal and death records, they will reveal a lot.I've been at this since 1986 and learn something new constantly.
So if you are serious here is a list of links which will help you in the search.The list includes links about Croatia, so you can learn a bit more about the country.
And here is my listing of useful genealogy links for Croatia.
NOTE: to use the on line phone books first select area code (zupanija which means county), then type in the name you are searching for next to Subscriber, then check the circle next to csz (this will allow use of English style keyboards), select 100 results and then click on query.You will see the list of names.The listings include phone number and mailing addresses and will also give you the correct Croatian spelling, with diacritical marks over csz.Be sure not to use the Anglicized or Americanized version I. E. ch or sh when searching.The page will also display as list of towns by county if you click on that bar.