My daughter did not sleep through the night until about 2.5 years old or more.
My son, is 28-29 months old, and he still sometimes wakes 1 time a night.
Each child is different. Totally.
Your son is now 3 years old, so you can't compare him to when he was younger.
EACH AGE stage, brings a change to the child. Each child being different. Sleep is not static... it changes ALL the time in a child, in a in a pre-teen, in a teen, in a college student, in an adult, in an elderly person.
At 3 years old and older, they begin to have different "needs"...and OFTEN they have night-time "fears." Different than when they were younger. And yes, they like to crawl into bed with the parents. Normal.
THen for your daughter who is 22 months old...well, she is approaching 2 years old....and they have TONS of changes at this time and throughout 2 years old. This is also when they get "night mares" and such and different manifestations of separation anxiety and what not. This is typically a "hard" age to get them to sleep or nap, anyway. But bear through it over the year... because it will fluctuate. It's developmental. It ebbs and flows.
For me & Hubby, we just kept to a consistent, regular, unwavering sleep/nap routine. EVERYDAY. EVERY NIGHT. And, though our kids had different challenges at bedtime, we never used heavy handed methods or punished. Our attitude was... this is normal kid stuff.. and we just waded our way through it. Sure, we had "rules" and routines... but we flexed a lot too. A kid is just a kid.
For my daughter, often times, she just liked to sleep on the floor for example. SO, we didn't MAKE her sleep IN HER BED like a statue. She could sleep where she wanted to... as long as she slept. So there were times like that too.
And we knew that when they were ready or able to...that they would sleep through the night. But yes, offering them consistency and a routine... this is what I find "helps" this child the most.
The main thing for us, was that they slept. Or sleep.
And, I also co-sleep with my kids, in variations, since they were born. For us, it's okay and not a big deal.
So, just find your groove, and the kids. There is no ONE method of making a child sleep all night. But a lot of it is developmental too... so these can cause a hiccup in their usual "ability" to sleep.
To me, there is no ONE thing that will make ALL KIDS AROUND THE WORLD sleep ALL night, EVERY night. Every night is different...and a different vibe.
And if everything for your kids are the same, meaning no major upsets or illness or stress... then it's probably just the usual quirks in kids.
All the best,
Susan