Possible New Country or Alliance

Would it be ASB if the countries of Estonia Latvia Lithuania and Belarus formed into one country or made an defensive alliance in case russia invaded? How about just Estonia Latvia and Lithuania? If these aren't possible what are some possible candidates for a new country close to russia?
 
The three Baltic states are in NATO, which is the best defensive alliance around. Belarus is basically a Russian puppet and has no reason to join with the others.
 
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