I’m no help. I was a smug first time parent because my baby was a decent sleeper at night for the first 6 months. I’d put her down and she would sleep. “She can self soothe!”. She was like that from the first day but sometime after 6 months it changed.
That same kid is almost 7 years old and if someone doesn’t lay down with her at bed time she will still be awake at 11pm. It’s been school break so we thought we’d try break the habit and haven’t been laying with her. She hasn’t gotten any better at falling asleep by herself before very late, it’s been 5 weeks…
My second kid was a rubbish sleeper. I spent the first year holding him in my arms for hours overnight and another year of very broken sleep after that. He is three now and will announce he is going to bed, take himself there and go to sleep. He wakes up once at night and quietly crawls into our bed for a cuddle.
I wish I knew what if anything we did had any positive or negative effects on either of their sleep 