A couple of questions first... Do they sleep with you, as in the same bed? Or are they in their own crib just in the same room with you? Same bed is a problem, same room is easy to fix.
Here is my experience...
My son, Max, is 18 months old and has yet to sleep through the night. My husband and I never put him in bed with us for two reasons 1. we're both paramedics and know the safety risks (SIDS increases to the 80ith precentile) when a baby sleeps with an adult, and 2. we didn't want to 'get that started' - we didn't want a 10 year old we couldn't get out of our bed (good birth control, however). He went to his own bed in his own room at almost 7 months old, but he continues to wake up at least twice and as much as six times a night. Being a 'make it all alright' type of mom, I quickly run to his rescue just to realize he doesn't really need me. His doctor told us to let him cry and only go check on him if he cries longer than 5 minutes (or whatever time we set) or if his cry is truly different. And eventually he'll learn to sleep through the night. No way! No respectable mother can listen to their baby cry for any amount of time and not go check. It's my belief that babies cry for a reason (and spoiled is NOT a reason). I worked an overnight shift just last night, and my husband called to say Max woke up only once. He let him cry, and Max was asleep three minutes later. A blood curdling scream would have prompted him to the rescue, but his was Max's usual nighttime routine. So Max showed us that he is capable of putting himself back to sleep, now it's up to me to be consistent with letting him. At least there a glimmer of light at the end of the tunnel = )
Here is my advice...
Your babies, on the other hand, are too young for this approach. They may be hungry, wet, hot, cold, gassy, sick, etc so the reasons for crying are different. Being only three months old, start making the permanent adjustment now. Put them in the same crib or bassinet or playyard because twins thrive on being with each other at this point. Being seperated stresses them out and they can help comfort each other too. That's a plus on your side. Max's doctor also told us to sit in his presence at bedtime with no contact. That's worked for us. As long as he can glance at me every minute or two while he's drifting off, he's happy. I don't have to rock him or pat him anymore. Just keep this in mind as your twins get older. Max loves his mobile that projects lights on the walls and ceiling, but at 3 months old, the stimulation could be enough to keep them awake. I hope some of this information is helpful to you. And my kudos on being a good mom especially with twins. I can only imagine!