Words of encouragement, plz. I'm just being Peanut Butter N Jealous :/

My SO and I had a miscarriage last year, I was 3 months pregnant and it was bad 😓 
Since then, my 2nd youngest sister (17) has my first nephew, my 2nd oldest (22)  is having my niece. And the whole time I am happy for them and helping them out with baby showers and nurserys ..... I'm secretly jealous.  Maybe it's not my time, yet. But I still don't know how to be fully happy for my sisters without missing my loss and being jealous when they complain about their hardships. I wish I had it 😢 I'm in no way better than them, but at the same time I'm older than them (24 almost 25) and I am mentally and financially ready for a baby. Any words of advice to over see my jealousy and/or words of encourgement to be the best aunt I can be!
Thanks for letting me vent btw!