How to get past your dislike of a soon to be family member?

Em
 OK!! I know I can't control whom my family members date, fall in love with, and marry. I also know it shouldn't affect me as much as it does. I would be very grateful if people could offer some coping strategies that go beyond "get over it."My brother-in-law (husband's brother) is living with MY parents. Yes, mine. We used to live there as well so we could get back on our feet & we did. But we brought my brother in law there & he's still there. He had a big heart and is sweet but lazy his room is always a mess and loves the attention. Literally doesn't do anything unless you tell him. I see him like my brother I never had but he's taking advantage. My parents are ministers and love to help people which is great! But I'm alittle jealous. My parents hug and kiss him. Something they never did with me. Also, he's been there for almost 2 years and doesn't pay rent. And I had to pay rent as soon as I started living there. I already spoke to my parents how I feel. They say I'm being childish. So there's that! 
Now, he's dating a woman who is like 27 and he just turned 20. They met at our church where my parents pastors. It disgusts me in a way because this woman was married and into drugs. And her ex (who has the same name as my brother in law) left her because she cheated. She tries to be the victim and tell people how people are always hurting her. Maybe she is changing IDK. But It's annoying. Not to mention, her laugh and voice annoys the heck out of me! And she has always disrespected me after I told her many times to leave my brother in law alone. He is begining to get his life together. And she still tries going after him. He just got out of high school. I am finding myself focusing more and more on how much I dislike and resent this woman, and it's making me literally dread having her as part of the family. They are not getting married or anything. I believe it's way too soon for that. But I think they made it official in dating. I'm already upset my brother  in law taking over my family & even more that this woman is trying to take over my in laws family. And kissing up to them...my husband is very supportive and tells me they will always love me because I've been in the family for a long time. And helped them. And I'm their first daughter in law/ sister in law. 
How to cope with this? I'm literally miserable about this. SORRY SO LONG! 😊