Most of us have a sense of humor. Sometimes, it's hard for others to detect, but that's another issue. Everyone, therefore, has a sense of what is humorous, and what isn't. You don't tease someone who is Italian about her or his family, for example. And you don't tease people from Latin-speaking countries the same way you would someone British, or Scandinavian, or German, who tend to reflect their cultural dispositions to be a little ashamed, and so they find embarrassment funny.
Do people with similar ethnic groups have similar senses of humor? You bet! This even shows in people's paternal DNA, or yDNA tests. For example, people from Norway, similar to other Scandinavians, have large numbers of ancestors from the Celtic (R1b), the Slavic (R1a), and the Mediterranean groups (I1 or I2, or Trojan). Slovaks, from Central and Eastern Europe, tend to have more of a very similar, closely-related Slavic background. The specific paternal haplogroup is R1a1a1b1a, of which most Slovaks come from a more refined version.
So how often do your family members tell jokes, and in what circumstances? I know from personal experience that people of Norwegian, Danish, English, and Slovak descent tend to be more likely to tell jokes, and laugh at the jokes of other, similarly-skewed people. I also experienced the opposite, as people of Irish, German, Welsh, Swedish, and Scottish descent did not respond as much to, nor share as much humor. American humor is more slapstick and relies on observational techniques. Canadian is similar, but with themes more specifically suited to Canadian history.
This is all interesting, because the type of Slavic paternal haplogroup Slovaks come from is R1a1a1b1a, which is also the same one that Slavic Norwegians come from. So, if the theories hold, the original Slavic ancestors came from the East, and eventually settled in what became Slovakia, then, probably telling and re-telling jokes the whole way, a group of them broke off, and emigrated to Norway. Maybe the Norway-bound Slavs played one too many practical jokes on the Slovak-settled Slavs. Maybe one group got tired of the other's collective sense of humor, who knew?