Yes and no.
If the brother wants out......for whatever reason. Like need money, cannot afford to keep, never uses, etc. And offered it to the OP at a fair price and the OP said no......(because as it is, maybe the brother is the only one that uses the garage, but only has to pay half the bills, taxes, upkeep, etc and dont want to take full ownership).....
Well if thats the case.....dont see where consulting a lawyer is gonna do anything but cost him money. Either buy the brother out at a fair price, or deal with whoever he sells it to.
Kinda like listening to someone complain if a a neighboring field gets lotted off in several 2-4 acre plots. And moaning about not having any neighbors within a half mile for years and now you are gonna have 10, ruining you view, etc etc. Heard that many times. If you dont like it, and dont want neighbors.....pony up or shut up.
Now this may not be the case. Maybe it was never offered? or offered at some crazy high price? This is what we dont know and want clarification on.
IF it was never offered or offered at a crazy price......yea.....lawyer.
If it was offered at a reasonable price and the OP refused......pony up or shut up.
But it also seems (and as many have said) that this could tear the family apart. Perhaps before going to a lawyer, maybe just sit down and talk with your brother?