Yes it is normal for a 3 year old boy to not be potty trained.
Boys usually take longer to potty train than girls do and so a 3 year old boy wearing diapers full time and not being potty trained is normal.
Some kids may not potty train and stop wearing diapers until they near their 5th birthday which is okay as well.
There's nothing wrong with anyone of any age wearing diapers and eventually they will get the potty training and use the toilet.
It is normal for a 3 year old to still wear diapers.
Although some kids are potty trained before age 3 years old it's still normal for a 3 year old to still wear diapers.
Some kids take longer to potty train than others so it's not a problem if your 3 year old is still wearing diapers and not using the toilet.
Some kids take as long as 4 years old to potty train and eventually the kid will stop wearing diapers on their own.
But if your kid is not potty training and nearing their 5th birthday then the potty training issue should be forced by taking the diapers away and dealing with accidents.
Eventually they will learn to use the toilet instead of wetting their pants.
It's even normal for a 2 year old and 4 year old to still wear diapers but they should begin potty training before age 5.
There's no age limit to wearing diapers and there's no age at which a child must be potty trained by.
All children are different and will potty train at different ages and forcing potty training will just make it worse and harder for the potty training to happen.
If you try to potty train your 2 year old and they refuse to use the toilet then just keep the 2 year old in diapers and try again when they are 3 years old.
I would not be worried about the potty training until the child's 4th birthday and then if they are nearing 5 years old and not potty trained then the issue should be forced.
But it's normal for a 2 year old to not be potty trained and be wearing diapers.
Lots of 2 year olds wear diapers full time and there's nothing wrong with that.
Kids potty train between the ages of 18 months to 3 years old and some kids don't potty train until 4 years old which is okay as well.