Buying house after seller breach contract with another buyer

[Christy George]

I am trying to buy a house for my brother. We found a sell by owner house and reached out to him. He said it is under contract but he is accepting backup offers. Few weeks later he called me and told me the other contract expired and the buyer didn’t act on the contingencies. He accepted our offer. 
Now I am hearing from my neighbor that that the other party is going to sue the seller. I don’t know how the other contract was written or what all were the terms. 
So, if the seller had breached the original contract, and is being sued, can it impact my purchase? 
what are the things that I should worry about and what are my options?