Jealous sister in law

I am in a relationship where i live with my spouse our son, daughter and his sister, we are together for the 3 years 7 months at the start of our relationship we bouth were with someone else and we both left that person to be togethe but because of that his sisters did not accept me and until now i am having serious problems with them. The sisters turn ther mother mind against me and some of his friends even though some of his friends realize that they are lies and we are now good friend his friends and i. I am the bread winner in the relationship i take care of the family financially and he will ensure the kids are fine we are perfectly fine with our relationship but the sister that lives with us in his house make our life a living hell since lately she even try to jeperdize my job and i get to find out about it and she still come in and preted as if she is not doing anything i need help because i do not know what to do in this situation. I am in a happy relationship for almost 4 years now and from i have known her i have never seen her in a relationship for 4 months some times i thing she is jeliouse of me and my relationship.