Certainly seems very strange, I have been a user of Skype for many years, and have many contacts who are in a variety of weird and wonderful places and have never had a problem calling them skype-skype, and quite rightly according to their website (
http://www.skype.com/intl/en-gb/allfeatures/skypetoskypecall/) calling to any Skype pc-pc is free, regardless of country.
Have you only just set up this Skype account? or has this setup worked before and now it doesn't? The only thing I could think of is if your brother-in-law has a Skype number you are trying to dial which one would require credit to call.
Have you tried contacting Skype and asking them?