Final answer:
The boy's family is likely to sue the Gregors for negligence, as they failed to install a fence around their pool, potentially causing foreseeable harm.
Step-by-step explanation:
The boy's family will most likely sue the Gregors for negligence. Negligence is a legal concept involving a failure to exercise the level of care that someone of ordinary prudence would have exercised under the same circumstances. In this scenario, not installing a fence around their pool could be seen as a failure to take reasonable steps to prevent foreseeable harm, especially when considering the safety of children in the neighborhood. If a court finds that a reasonable person would have foreseen the danger of an unfenced pool and taken action to prevent access, the Gregors could be held liable for the boy's injuries due to their negligence.