IS THERE ANY WAY OUT OF A SALE OF HOME CONTRACT?

My brother worked for a company for 30 years and they recently folded. He has four kids and is in a tough financial situation. A real estate agent convinced him to sell his home at a "priced to sell" price and it sold in a week. (about three weeks ago). He has since had an offer from a few people offering 100K more and they don't even need a mortgage. Is there any way out of the original contract?? He really needs the extra money since he is still out of work and has kids. Any info will help. Thank you.