House purchase, from the grandparents to the grandchildren

Hello. Maybe a word from me on this: It’s not actually about driving the price down to negotiate my grandparents' cost. But the lower the price is set, the less likely it is that the purchase price can be disputed later. If the shares are only worth 100k on paper later and I still pay 120k, then I have actually bought the house above the assumed market value and can relax if any of the heirs think they didn’t get enough inheritance – you never know. As mentioned, there has been no contact for decades. These people probably aren’t interested in a good relationship. Since I can’t provide care, as my grandparents will look for their new home near my parents (1 hour away), I don’t know if the option would be suitable for me. Probably not. And I don’t want to rely on questionable luck. Happy holiday!