C.N.
I do not have twins and my daughter is my first child. She just turned 2 and is not yet fully potty trained. However, when we are at home, I allow her to run around naked. She goes and uses her potty which I've moved to be near her play area so she doesn't have to go too far. And she uses it regularly. She can't unsnap her pants nor pull them off by herself, and since we don't have any of those crotchless pants Asian countries use, we've just gone with the naked girl routine.
We use a cloth diaper service, so since when she was 3 months old, I became aware of when she needed to go. And we often timed it so that every hour, we took her to the potty to let her pee. So she understood the concept from early on. But lack the motor skills to do it by herself until now.
I would say make the time and effort to try to time when they need to go and encourage them to go. The first three times, we did the naked girl routine, she had a few drops that hit the floor before she headed to the potty, but she learned pretty quick. So just applaud them when they display any indication of wanting to potty and give them time. Every child grows at their own rate.