Is blood really thicker than water?

Ok, heres the scenario. You're walking in a forest with your sister and the person in your life who you call babes. You're having a great time and the three of you are singing songs and throwing rocks at the filthy crows in the sycamore trees.

Suddenly out of nowhere a large man with a large gun jumps down from a tree and says in a voice that sounds very much like Adam Ant.

"Halt! Listen up and listen up good Pighead. I'm going to kidnap one of the two girls that stand here beside you and there is a chance that you may never see her again. I realise this is a horrible thing to hear so as to make it more bearable I'm going to let you decide which one I take"

It's at this stage that Pighead's brain starts buzzing with confusion and terror. What a horrible choice to make. Give up the girl who you have shared a bed with for most of your adult life or give up the girl you met four years ago who made you the happiest Pighead in the world by agreeing to become your girlfriend.

Unfortunately one of the girls has to be given up as the large bloke with the large hands has since informed you that he is invincible and there is nothing in the world that can stop him taking one of your girls. Just Pigheads luck that this bloke turned out to be invincible. Looks like one of the girls is going to have to be sacrificed.

To be honest Pighead would have to say he'd reluctantly give up his sister. Nothing personal against the girl as she's a great lassie but time and circumstances have dictated that she has falling down the pecking order of loved ones in Pighead's life. sounds harsh but thats the kind of world we live in. A world where water is sometimes thicker than blood.

So who would you give up?