Tying to think positive

I’m home for Mother’s Day at my parents condo that my brother and sister-in-law also live in. I get up this morning and my sister-in-law proceeds to tell me she is pregnant, of course I get excited and then a semi truck of emotions hit me since my husband and I have been trying for almost 2 years and they get pregnant on cycle 2. The hardest thing yet is that I was there when she told both of my parents and my mom who has early onset dementia lost it with emotion. I feel like I got robbed of her genuine excitement as one of my biggest fears is that she won’t be around for when we have a child. I’m the older sister and I feel like my brothers life is passing me by. I know and continue praying that God has a plan for me/us and I’m trying to genuinely be excited to be an aunt for the first time but feel like I’m dying inside.