Big Macintosh knows he has a cousin named Braeburn, he knows that he lives in Appleloosa a thousand miles away, but he doesn't know the pony himself, not really. Perhaps the fact that his cousin rarely visited is to blame, or it could be because of his extreme shy nature that he isn't close to his own family member.
Regardless of if he is well acquainted with his cousin or not isn't the issue, the issue at hand is that his cousin is coming to visit, trying to get his life together once and for all with family breathing down his neck to finally settle down so not to end up a lonely old stallion.
While trying to be supportive of his cousin, Big Macintosh finds himself growing closer to the yellow coated fellow... perhaps a bit too close.
Incest is Wincest, don't like don't read.