Future Sister-in Law getting engaged at the same time as us

Hey there so I’ve had this pretty heavily on my mind and I really just want to make sure that I’m not wrong for feeling the way I do about this.
My fiancé and I have been dating for 3 years and got engaged in October of 2019. We decided to have a bit longer of an engagement to allow us to settle down into our new jobs post college and wanted to plan for September of 2021. His parents held a special engagement dinner for us shortly after getting engaged where his younger sister and her boyfriend who had been dating for only 6 months at the time began talking about when he would propose to her (what type of ring he should get, how he should do it, ect.). At the time I wasn’t super bothered by this but here we are about 6 months later and he is about to propose to her as well.
Their proposal to her has already taken priority over our wedding even though we were engaged first. His younger sister is already well aware her boyfriend is soon to propose to her and has begun loose planning with her mom. I get that everyone is excited for them and I am as well but I can’t help but just feel a little bit hurt. They aren’t even engaged yet (it’s happening on Friday) and have already talked about how it will be before ours in May and a destination wedding. We have been told by my fiancé’s mom that we have to put a deposit down on venues now so that her daughter can plan, even though my parents do not currently have the funds to put down a deposit in the midst of this COVID-19 outbreak. We have also made the concern that we do not have the extra time off that year to be able to attend another destination wedding as we have already committed to one earlier in the year and have to plan enough time off for our own honeymoon. We were told by my fiancé’s parents that we are just going to have to make it work even though they are not even engaged yet and we had already had these plans for a long time.
I’m just a little frustrated by this whole thing. My fiancé and I have not been able to plan much due to COVID and my parents current finances and I just feel like we have been put on the back burner by his family. I get you’re naturally going to be excited for your own daughters birthday, however it has taken so much priority over ours already when my fiancé is the first born. And it also hurts looking back seeing that they brought up their engagement at our engagement dinner. Just seems wrong to me. We’re both just extremely hurt by the situation and aren’t really sure what to do. I plan on sitting down with my future sister in law after she’s engaged and discussing my concerns with her as I’m not sure how much is her and how much her her mom. But none the less we’re both just less than thrilled about everything that has happened and it’s really giving me a hard time. I want to be happy for them but I still can’t help but feel a bit upset and as if no one even cares about our engagement in the first place.