Hi S.,
My twins are now 25, so trust me on this: they are ready to be potty trained. My son started tossing his poopy diapers behind the sofa. I was ready to thrash the puppy, but it was him!
Get dual potty chairs, if possible, and this will go easy.
Get some disposable pull-ups. I recommend Seventh Generation, which is what I buy for my grands. Those biodegrade, and so won't be here long after we are gone. You can get great prices and delivery at diapers.com
Put on the pull ups and announce these are big girls panties. Make a bit of a to-do about them. This is a good thing.
Time their poops for a day or two -- they should happen about 15 minutes to half an hour after a full meal. THEN BE READY!
When they get that concentrated look on their face, announce to them what they are doing, so they will associate the deed with the sensation.
Then quickly, but without stressing, put them on the potty and tell them what good, wonderful, smart big girls they are to put their stinky poops in the potty. Applaud when they go! Sing their praises!
Do the same thing with peepee, and in a couple of weeks, your house will be diaper-free again.
They may need pull up over night for a while, but taper off the evening liquids an hour or so before bed, and that will resolve itself.
Be patient. If they have good motor control of their legs, walking and running, they are ready.