I'm so sorry for your loss and that your little sister is pregnant first. I wanted to share my story in hopes that it makes you feel like you're not alone.
First, let me say it's perfectly understandable to want to have a baby first if you're older than her, I was the eldest in my family and my sister was 20 months younger.
My sister married her high school sweetheart at 26, 10 years after they met and had dated all that time. Going to college without my own future hubby was so hard so I felt rushed to marry, knowing my sister could conceive way before me. I got married at 21 to a Turkish guy doing a phd in petroleum engineering. 2 years later we divorced (his parents wanted a Turkish bride and he was wishy washy). I was heartbroken since my sister was engaged it was so hard and I still had no kids.
I thought God would make me an old maid!!!!
But, then the unthinkable...I reconnected with a guy I knew at 19, my absolute dream. We married at 24 and got pregnant on our honeymoon.
My sister married at 26 and got pregnant after that.
However, my husband decided he was one and done. For the last nine years until we got shockingly got pregnant Jan 1 and Mc'ed on the morning after pill. (I had taken it within 12 hour per my husband's one and done feelings---he pulled out for the last 10 years but felt some got in that day)
It was soul crushing in the last 10 years to watch my sister have baby, baby, baby---3 girls aged 7, 5, 3....I have one amazing 9 yr old son though.
I just wanted to tell you I really get it, especially having had the MC. We're now on TTC cycle 3 after waiting 2 AF's and I'm getting so depressed.
But, I remind myself that God has a plan because now my husband has changed his mind and my precious miscarried baby who is buried under our oak made it be so.
If you ever want to talk I'm here...
What you feel is completely normal, you grew up wanting the first grandchild..