I need Advice (Parenting)?

Basically I need advice... I have never met my Dad although I before I was born he hit my mum. It's a sore subject however, now I really want to met / talk to him how do I approach my mum what do I say. She might be annoyed as she hates him from what he did and so does the rest of my family... But how do I get across the point that I wan't to meet him now and that they shouldn't necessarily forgive him but allow him to be in my life for my sake. How do I make them realise that that is what I want. How do I keep them calm about the situation. How do I persuade them if they say no or just make them understand how I feel? I'm Fifteen by the way (Sorry for the amount of questions its urgent)