Can family illness be used as a reason for green card holders not to come to the United States for a long time?

Yes When considering whether to grant entry, the immigration officer will consider the length of departure, the purpose and motivation of departure: if you have left the country for more than half a year, do you have permission to re-enter the United States? Is there any evidence to prove the special reason for this long-term departure? For example, getting sick, taking care of sick relatives, and dealing with real estate. As mentioned above, green card holders who have left the country for more than six months need a re-entry permit to the United States, but if the parties concerned are not inextricably linked with the United States, it is not enough to rely solely on re-entry permits and green cards to maintain their green cards.