How do I sweeten low cash offer deals for seller?

[Mary Ann]

I have a house in Brooklyn. The family is selling it, but the cash offers are low. It is valued around 700K, but the cash we are getting is around 500s. How can we sweeten the deal? Are there any contingencies or other "sweeteners" we can ask for in cash to help family move, or make up for the low offers. They don't need to be at 700k, but they need to be in the 600s so fam can walk away with something, or get something else to make up for the deficit. Any info is appreciated!