You really don't understand women Andy; if you cheat on her with a neighbour, she can move, if you cheat on here with her best friend, she'll blame her friend more than you, but if you cheat on her with her sister, she'll hate her sister for ever, and hate you even more for breaking her family up.
Of course, sisters and mothers gets you brownie points with your mates, so sometimes it's worth the risk.
Of course, sisters and mothers gets you brownie points with your mates, so sometimes it's worth the risk.