Actress Mila Kunis (42) talked about the secret of her happy marriage in the talk show "The Drew Barrymore Show". The 42-year-old revealed that her long-standing husband Ashton Kutcher (48) had been her best friend since her youth together – and that's exactly what makes her being together so special. The two of them got to know each other on the set of the cult series "The Wild Seventies". According to Mila, it's above all this decades of famil…