G., Unfortunately, many boys are not ready to potty train until about three to three and a half. Take your focus off something they really are not old enough to control. It will happen in a natural way. When they get to school they will not want to be the babies in diapers. In the meantime focus on what they can do well, rolling a ball,using a spoon, or fingers, using a sippy cup, pretending to read or eat their books,. give them lots of praise for the grown up things they do.
Like many issues in boy's lives, they will be potty trained when they want to be like daddy, and not one minute before, My son has full charge of his little guy using the potty, it's a perfect daddy job because they have the same equipment.
When you signed up for twins you did not ask for the wimp position, and you will succeed if you don't create an issue.