A lot of people I know who teach at the college or university level--adjunct instructors, TA's, professors--point out sardonically the tendency of students to request either time off or extensions on assignments because a relative, usually a grandmother, allegedly passed away. Some of these teachers claim to know of instances where a single student made multiple claims in multiple semesters about the same person dying. As a general rule,these teachers make up ironic stories about how dangerous it is for people to have their grandchildren go to school, since it seems to increase their (the grandparents') chances of dying expnentially.
I have laughed at some of these stories and other jokes that poke fun at the phenomenon of allegedly spurious claims of deaths in the family, but ultimately I think these jokes are disrespectful of the students and should be avoided.
People do die, and death is serious, and we simply don't know in any given individual case that the student is simply making it all up. Most "traditional" college students are at the age when their grandparents start dying. (One of my grandmothers passed away when I was a junior in college. My other grandmother passed away at a time when my oldest brother was of "traditional" college age, even though he chose not to go to college.)
For the sake of argument (but only for the sake of argument), I'm willing to stipulate that 9 out of 10 claims that a relative has passed away are false. I remember one situation in which I had my own private doubts that the student was making the whole story up. (I, of course, didn't challenge my student to produce "evidence," but something in they way she told me what happened suggested to me she was lying. I should add, however, that I have no idea--other than a "hunch," and unlike others who are so confident in their intution, my hunches are wrong at least 50% of the time--whether she was lying.) Even granted this, I think such jokes are inappropriate.
Still, I think the jokes are inappropriate. They encourage a disrespect for the students and almost an expectation that students will be immature.
I will say that in practice, my teacher friends take students claims seriously and respectfully when they're presented with an individual case. They give the time off or extensions as needed.