PLEASE HELP! I'm in Love with my Sister's Husband. What can I do to make Him divorce Her and marry Me?

What can i do to make them divorce?

Dear friends,

I am a 23 years gal.

Have been in a relationship with my sisters husband for 5 years now without my sisters noticing, sometimes we stay together, sometimes i stay away from them.

It started immediately i cleared my high school.. I don't know how its happen but i felt in love with him because he was my 1st man, up to now i love him and he too loves me. I'm almost clearing my university studies only some months remaining... I have told him to break up because i dont want my sister to know this but he insisted on marrying me!

I'm totally confused by now because i need 2 settle after my studies.

What can i do to make them divorce?

Is there any strong witch craft who can help?

Advise me please.