Vowed to get rid of it this year? Many moms of twins battle the floppy flap that hangs over the jeans long after the births of their babies. The “twin skin” club is exclusive and members love to share their strategies in toning the tummy. So keep talking and start crunching. Either way, misery loves company and you’ve got lots of it. If there’s one thing any mother of multiples can testify to, it’s this: Your body is never the…