I feel my experience is relevant and might help so I'll share honestly.
I always suspected I was autistic on and off from my twenties and also my mum. These days I feel it's more like adhd, but I've never had an assessment.
Faat forward to having dd1. She was a high need baby, never stopped crying, but then turned into a very quiet, albeit sensitive, baby at about 6 months.
I knew from day 1 she was different. She was completely delightful, but super intelligent and verbally advanced, whilst missing all her physical milestones like crawling, walking, jumping etc, as well as being very averse to change and very shy.
I decided to have another, because I worried that she would be a lonely child and have no friends (tbh a bit like I would have been at times without my siblings).
It wasn't just that obviously, I had always thought we would have more, but I knew that I was stretched, even by one.
Anyway, it worked out brilliantly. I had another dd and the age gap is 2 2/3 years. It was very, very tough when they were both tiny. But once they could play together, they bonded so closely together and we're inseparable.
There were issues between them at times. But generally they have both been gifts in each other's lives. Dd1 has literally just got a diagnosis of autism aged 21. I tried so many times in childhood but each time was fobbed off, delayed, obfuscated, screened out. In the end, dd1 decided she'd had enough of being messed about.
All in all, I'm eternally grateful for my two daughters.