Supernatural's Sam and Dean Winchester are notoriously unlucky in love, but Jensen Ackles and Jared Padalecki claim that is entirely by design.

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The hunters live their life on the road and anytime either of them exhibit a desire or a need to settle down, their plans ultimately come crashing down around them. Two of the boys' more recent relationships - Sam (Padalecki) with Amelia (Liane Balaban) and Dean (Ackles) with Lisa - provide prime examples of this problem.

"I was never a big fan of [Sam and Amelia]," Padalecki recently explained at Rome's fifth annual Jus In Bello Con. "I understand why the writers needed to do it, but I think the writers actually wanted to set it up to fail."

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And fail it did. Somewhere between the reappearance of Amelia's husband and the return of Dean from purgatory, the pair's relationship fell apart.

"Another way of telling a story about how the brothers did need to be loyal to each other is by putting them in other situations where you get to see it's not giving them happiness, you know?" Padalecki continued. "Sam wasn't happy with Amelia...It was written to be kind of a false attempt at having a real life, like with Jessica."

Just as Sam ultimately chose to leave Amelia behind, Dean left Lisa and Ben when his younger brother spontaneously emerged from the cage.

"It was an attempt to show the audience that these guys can never truly be outside of the world that they live in...in the end it's always destined to fail," Ackles explained at Jus In Bello V.

As a tribute to the boy's failed romantic relationships, we've put together a slideshow of their previous girlfriends. Scroll through the photos above to see some of the Winchester's former love interests.

Supernatural will return to The CW this fall.