The Inlaws!

I have the most wonderful husband and I like my in-laws, except I can’t stand my brother in law and his wife. We have had difficulties in the past, but I no longer get crossed when I think about those, they are in the past. I don’t speak to them and actively avoid them ( I know I should be taking the invite to the classroom instead and challenge myself!).
I thought I have got over them and I wouldn’t care very much what happens with them but I realised I do. To my embarrassment, I get in a mood every time they are mentioned and when I think they can be happier, or more successful than my husband and I! I know how irrational are those thoughts as what matters is that I am happy with my lot.
Every time a thought about them crosses my mind (which happens so much, which makes me think I secretly like to get my knickers in a twist) I have tried to figure out why I found them so annoying and I have come to the realisation many of those thoughts are rooted in jealousy, which I find rather unpleasant.
I am ashamed and tired of my feeling of dislike towards them, I want to feel love towards them but I only find feelings of dislike (which is embarrassing and immature and really don’t serve me). I am finding it really hard to change my thought process and curiously every time I try to make a model about them I find it overly hard.
My question is how I can tackle these thoughts and feeling? Should I be focusing first on my thoughts about them? or my overall thoughts of jealousy/envy/ scarcity first? I am worried that these thoughts are so deeply ingrained that even if I managed my thoughts about them those thoughts might come up again towards other people?