Newbie. Signed a contract for a house with squatters

[Gytenis B.]

Hey all! 

Got my first contract for a property! Woohoo! 

Details:
House got deeded to one of the daughters by her father. He passed away shortly after. Her sister and brother "temporary" moved in to the property. Moved in and lived there for the last 2 years and did not react to any requests to move out. Owner (the sister who got the property deeded to her before father died) got tired of all the mess and decided to sell it. Posted the 30 day notice on the door. 

I signed the contract to buy the property before squatters moved out to get a better price and not risk loosing it to some other buyer. 
30 days notice was posted on July 8. The squatters (brother and sister of the owner) told they will be out by the end of the month (I doubt it because they made such promises before).  

How would you deal with this kind of situation? Would you go ahead and purchase the property and deal with the situation yourself? Would you not try to get in the middle of this? Can you take over somebody's else started eviction process? ...or would I have to start over again if I purchased this property? 

Any advice is appreciated.