How old is he ???
Did I read this correctly in hi schedule ... he gets TWO baths a day? One first thing in the morning and one right before bed?
If this is true - there's 2 (or three) issues with that which could be contributing to the issue:
1) Children simply do not NEED two baths a day ... it's very drying on their skin (even if you slather them with lotion post-bath and even if you don't use soap) . Unfortunately, parent's/caregivers (influenced by ads by "Johnsons&Johnsons" I'm sure) often think that in order to get clean a child needs to use soap (at every bath etc)- this is simply not true. Infants and young children don't really sweat (unless they have a medical condition) and as such, simply letting them sit and play in the bath for a while, while using a hand held shower to rinse their upper body or a plastic cup to pour water over them etc, then "washing" them by wiping well with a soft cloth and warm water is really all that is needed, most of the time. Once they are out of the tub, it's very important to make sure they get a hypoallergenic gentle lotion applied to their entire body (minus hair and genitals of course) to help lock in moisture etc.
2) While every kid is unique - personally,The nap times and lengths might be contributing to the night time issues - you say he's been on that schedule for 20moths ? It's likely he really doesn't NEED that much nap time anymore (especially in the afternoon).
My 15month old niece has a morning nap that is between 1hour and 90mins and IF she has an afternoon nap it's typically an hour or less - and we make sure that she's awake before 3pm so that by bed time she's really ready for a good, long sleep. I'd recommend seeing if they can move up the afternoon nap and make it shorter so start the nap at 1:30 and end it at 2:30 at the latest... that way there's more time between the nap and bed.
MOST importantly
3) If someone's bathing this child when they wake up and get dressed to START the day, and then is bathed and then dressed (in PJs) to END the day ... there's a major mixed message being sent to this kid as far as routine goes. Typically, it's a much better idea to bath a child at NIGHT only - as part of a larger "bed time routine" . The reason having a consistant unique "bed time routine" is so important is that it is how infants and children shift from "it's day:it's time we play, we nap, we play again" to "it's night: it's time to slowly relax, and sleep for the night" mode. Right now his schedule doesn't make a bid enough shift to cue him and his body on what's suppose to happen.
Ideally, you want to have it so he has a specific and unique "wake up" routine, then daytime routine and then a specific night routine.
You might have something that looks like this:
6:00AM - wake up, diaper change, get dressed, have breakfast. (NO BATH)
7:00AM - leaves for babysitters etc
9:00AM - nap 1 hour
10:00 - 11:00 Play Time
11:00 - 11:30 Lunch
11:30 - 12:30 independent play time
12:30 - 1:15 reading time with caregiver (or other "quite time" educational activity)
1:15 - 2:15 Nap Time
2:15 - 2:30 small snack (fruit, veggies or meat/protein)
2:30 - 3:00 active play time
3:00 - 4:00 Mom picks up from babysitters
4:00 - 5:00 Play time (specifically with mom for at least the first 20mins)
5:00 - 6:00 Dinner
6:00 - 7:00 Play Time
7:00 - 7:45 Bath time, get dressed for bed, brush teeth etc
7:45 - 8:00 "good-night story-time" with mom (&who ever else wants to be there)
8:00 - Bed Time
You'll note some really important time shifts I've made, and specifics I've added beside various play times, etc. These might sound like they "don't really matter", but they DO. They form a specific routine that happens that allow everyone to transition from morning, into day then into night.
Also, pushing back the evening meal might be odd at first, however it does two important things ... it creates specific "mom and son play time" first thing when they got home so that they actaully spend some TIME together. Eating later means that he's also not going to wake up hungry in the middle of the night - kids burn calories FAST and expecting a child to go more than 14 hours between meals (possibly without food at all) is not a great idea and pretty much sets up a situation where the child is (legitimately) waking up hungry in the middle of the night.
Having a solid bed time routine ... such as:
PART ONE:
eating dinner, quiet play/colouring/playing blocks etc (nothing too high energy as this is "wind down time"), then bath time, brush teeth, get changed and ready for bed (I'd recommend doing all the diapering and putting on PJs in the BATHROOM (so that when you enter the bedroom it can transition into "part two" which is when you go from "light, active etc time" TO "dim, quiet, gentle, etc time"_
PART TWO:
In the bedroom - if they're in a bed, then lay/sit in bed together...if they're in a crib then in a comfy chair or sitting on the floor on some big cushions or a foam sheet/mattress etc.
Have "quiet talking time" if they're old enough to tell you what they did today, then ask them what they did, what their favourite things where, discuss what will happen tomorrow etc. If they're pre-verbal then you can recount parts of the day for them (what they would have done etc) as well as tell them about any family members etc ... basically this is "connecting time" - just make sure it's quiet, relaxed, restful ... not jumpy, etc.
This is NOT the time to discipline etc them about something they might have done "wrong" or "bad" during the day (that just creates anxiety) however it IS the time to offer praise for things that they have done well/"good" (good listener, good helper, etc - try to name specific things even if it's "you ate dinner so well" or "you did a great job of sharing today, I'm very proud of you" etc).
Once you've had some sharing/talking time, then it's a great time to read a story (or a few short books) together... For short books (board books, 5page books etc) then I usually pick 2 or 3 books to read together. Ideally the child is actually starting to fall asleep while you're reading the last book (part of a longer story) - so if you read a religious story nightly and say prayers as part of the routine then I'd actually recommend doing that as a transition from "talk and sharing time" to "story reading time" and then once that's done read any other stories etc.
Doing this creates not only a routine that makes sense to the adult AND the child (which means if a babysitter ever puts them down if they follow that "routine" it should work quite well, instead of dissolving into chaos) it also give the child and the parent(s) some quality time together - which is very important for everyone.
I hope that helps some ?
Every child is different ...however having looked after a LOT of children, as well as being one of the primary caregivers for my niece, there are a lot of things that tend to work for almost all kids, the above being those "things".
I mentioned in another thread - that I really honestly think that you and the boy's mum would greatly benefit from taking a parenting class together. The classes aren't for "bad parents" - they SHOULD be for EVERY parent! There are soooo many things that you need to know when raising children and having additional resources and supports is critical. Taking parenting classes not only teaches coping techniques, and how to manage developmental advancements but also important skills like how to tell if your child is really sick (when to go to the dr, when to go to emergency, when to call 911 - and sometimes it's not nearly as "easy to know" as you'd think) also things like first aid, CPR, info on how to give medications properly, how to make sure your home is safe, all types of VERY valuable information that even the best parents can learn from. It also allows you to meet other parents in the area who you might be able to look to for ideas, play dates, peer support, info on good docs/good schools/various programs available etc.