Our society puts a lot of pressure on parents to potty train their kids before the kids are capable to be potty trained. And every kid is ready at a different age. It has nothing to do with their IQ. Some kids are ready before their 2 years old, other kids are not yet ready until they're 5-6 years old, which is normal. There's a huge variation there and it has nothing to do whether they're smart, how good a parent you are, or the combination of genes, and all other unrelated reasons.
Potty training can be a exciting or frustrating to any parents. The worst thing to do is to pressure the kid. If the kid isn't potty trained, you tried, but it's not working, that's okay, it's not the time yet. As long as you got no problem with it, the kid is healthy, and you have a happy family.
Believe in waiting until a child is ready and not being discouraged if you are not seeing any progress. You don't want this to be stressful for your child and you don't want it to become a power struggle. Nothing good will come with forcing a child. Have a break and just try again.
Make the training as natural as possible. It's a natural thing, have fun with your kids, model it, and it will happen.