for your dad and mum problem I think you needed to talk to someone more professional!
but for your friend you can sit down a talk to her! tell her why you don't think its a good idea for her to go out with your ex's but that all you can do and well its goes from there she will talk it or leave it!
Hope It Works Out For You

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No one is too young for love, because love doesn't come from your mind, which knows your age, but from your heart, which knows no age.