A black woman has five children who all look alike. She names each of them Tyrone. How does she tell them apart? Their last names.
Why do you think that joke is funny?
I think that if people just named their kids normal names, it would be easier to distinguish them from one another.
It is impolite to judge what other people name their children, especially when you generalize about an entire group of people based on their race. Also, it is racist to assume that if a Black woman has multiple children, then they have different fathers. You should try to avoid telling stereotypical jokes like these, as they can be hurtful.