Proof that Bret is the Older Brother!
I assumed--as well as most people--that Bret is the older brother, but no one ever had any proof on whether or not it was true. Well, I have it, from Bret's own lips in season 3's episode, 'A Flock of Trouble':
Verne Scott: "To Mr. Maverick, who will find that lightning can strike twice in the same place."
Bret: "That's just what my pappy said as he looked down in my brother Bart's cradle."
The obvious meaning is that lightning struck once when Bret was born, and struck a second time when Bart was born, lol!