IS THERE ANY WAY OUT OF A CONTRACT FOR SELLING YOUR HOME?

My brother is in a bad financial situation because a company he worked for for 30 years suddenly folded. He decided to sell his home and downsize because he could no longer afford his mortgage payments. He sold his home in three weeks because he priced it to sell quickly, but was recently offered $100,000 more by a neighbor who could pay without even getting a mortgage. He is very upset because he has four kids and really wants to be able to take the higher offer. Is there any possible out of a contract for a home sale? Any info would help.