for a little extra fun, consider this case, which sounds kinda skeezy but totally isn't.
two brothers in a small town fall in love with and end up marrying two women who happen to be cousins. (think of it as two trees growing near each other and their branches becoming intertwined, like this only at two locations on each tree instead of just one. definitely not the same tree looping back on itself.)
one of the resulting kids—let's call him "CCG"—has a cousin (well, two, but...), and we'll call him "Pebu". CCG traces up through his father and Pebu's father, landing on the grandparents they have in common. "but wait", says CCG's mom, "your aunt and I were already related to each other before we got married!" so CCG traces up through his and Pebu's mothers this time and finds great-grandparents in common. "you're right," he says, "Pebu and I are also second cousins! and my aunt is also my cousin once removed! boy, does that sound skeezy."