My mums dead, I would have hated for her to find out about my cutting but she died before it got too serious to hide, I think if she had of found out she would have flipped on me and been really upset
My dad, I told him after an argument with my step-mum, I just told him that I'd been really depressed lately and that I'd been to the doctors and given anti-depressants and after he was cool about that I sort of mumbled that I cut myself sometimes when things get too much
He was just really shocked but he was supportive of me
He doesn't like talking about my SI with me because I know he gets nervous because he doesn't know what to say to me, but on the whole he is very supportive, but I still find talking to him about my SI too awkward
He saw my scars and cuts when I got admitted into a pych ward and he seemed a little bit shocked and upset then though
My sister is the other family memember who knows but she found out by accident when I cut in a rather visable place one day
She just asked me outright if I'd been cutting myself and I had to come clean, she was pretty calm and cool about it, even though I think she thinks I'm stupid for doing it
I'm rambling now

On the whole I think telling your parents is a good idea if you know how they usually react to stuff like this, I know my dad is usually cool as a cumcumber so I didn't mind telling him too much