Best wishes to your brother/cousin! Ukraine has got to be a difficult mission and I wish him all success!
There is something about a missionary that has him completely set up for future life - and adding an extra language has got to be one of the best job skills going!
I hope you can some day serve a mission too.
I want to serve a mission too, just don’t know where I want to go yet, Its not like I can choose though XD
You will be sent where you are needed most. However, I do believe they take into account current talents and skills, so if there is a place that is close to your heart, learn all you can - especially language and cultural things. Doubly important if that's a place the Church is trying to expand - so if you want to serve in the Ukraine, learn Ukrainian.