Most children begin potty training sometime around 18 months to three years of age, so yes, if he is otherwise growing and developing well, it is probably normal that a 2 1/2 year old does not want to use the potty.
Although many parents feel like 3 years is a magic age by which their child must be potty trained, that is not always the case. A recent study showed that almost 25% of kids weren't potty trained until they were 3 1/2 or 4 years old.
Even in an older child, it is important to look for signs of readiness before you begin potty training, including:
•staying dry for at least 2 hours at a time •having regular bowel movements •being able to follow simple instructions •being uncomfortable with dirty diapers and wanting them to be changed •asking to use the potty chair •asking to wear regular underwear.
You should also be able to tell when your child is about to urinate or have a bowel movement by his facial expressions, posture or by what he says. If your child has begun to tell you about having a dirty diaper you should praise him for telling you and encourage him to tell you in advance next time.
Even if your child isn't totally ready to begin potty training, you can still get him a potty chair and have him decorate it with stickers and sit on it with his clothes on to watch TV, etc. to help him get used to it. Whenever your child shows signs of needing to urinate or have a bowel movement you should ask him if he wants to use the potty or take him to the chair and explain to him what you want him to do.
Only keep him seated for a few minutes at a time, don't insist and prepared to delay training if he shows resistance. Until he is going in the potty, you can try to empty his dirty diapers into his potty chair to help demonstrate what you want him to do.
Another good technique is modeling, where you allow your child to see family members or other children using the toilet, and using observational remarks. This involves narrating what is happening and asking questions while potty training, such as 'did you just sit on the potty?' or 'did you just poop in the potty?'
Things to avoid when toilet training your child are beginning during a stressful time or period of change in the family (moving, new baby, etc.), pushing your child too fast, and punishing mistakes (treat accidents and mistakes lightly). Be sure to go at your child's pace and show strong encouragement and praise when he is successful.