@saffkey1
How you feel is how so many of us feel. My DC with autism is older than yours and impacted severely as well. Love is no different, it's fierce and wonderful and that's a good thing! But almost everything else is. We deal with not being able to go to communicate events as a family, having to miss siblings school plays (one is very active in drama club and has never been able to have the full family there - also I have to stay with sibling as no one can baby-sit), a severe restriction on days out and travel, special days like Christmas and Easter are often accompanied by severe meltdowns due to the change in routine. I watch friends children 1/3 my DC's age doing things that my child can't. The grief is still there. And as everyone gets older the worry about what will happen in the future as parents age is profound.
People don't get it, a friend recently criticized a family we both know with a son with autism in his 20's who were searching for live in accommodation for people with disabilities. This same friend's children are away at Uni. She was clueless as to the pain the parents are in, one parent with a life threatening condition. Trying to figure out what to do because there will be no Uni or moving out in the traditional way but they will age and possibly not outlive him.
It's hard. I won't lie. We are in a hard space right now dealing with aggression, sleep disturbances and more. It's like the elephant in the room sometimes, your child's life so restricted, with so much less possibilities. Acceptance and love doesn't mean you don't wish you could change it. My child's life is so hard. So full of angst. I would give my right arm to change things.
As for siblings we heard from our developmental Pediatrician that often siblings struggle. Mine are older and would say it single handedly is the hardest part of their childhood. It's impacted so much of our lives and the one closest in age and more involved (by choice) said she understands why families burn out and can't do it...
Having said all that the love is so deep, so profound. And that carries us through the very very hard.
You aren't being unreasonable, how you feel is so normal!