Potty Training HELP

I have almost 3 year old boy/girl twins. DD almost completely potty trained twice and regressed both times. She knows to use the potty but just won't. I have tried putting her on the potty every 20 minutes (she'll say she can't go and then pee or poop as soon as she's off) I have tried rewards, she's not interested. I have tried letting her go in underwear and pee/poop in them and it doesn't phase her one bit. She DOES show interest in the potty and knows her cousins (who are around the same age) are "big kids" because they use the potty but she just won't use it.

DS is delayed developmentally (DD is not) and has been in EI since he was 18 months old. I really feel he is no where near ready to potty train. I feel that maybe DD won't use the potty because DS won't? Should I just drop it and let her do it on her own? (Which I intend to do with DS) I'm just so sick of hearing people say "They're not potty trained yet?!", "My DD/DS was potty trained at 10 months!!" Blah, blah, blah. I'm sure it's different potty training twins vs. a singleton but I'm frustrated. Any advice? Thanks ladies.

Quoting ♥TwinsRock25♥:" I have almost 3 year old boy/girl twins. DD almost completely potty trained twice and regressed both ... [snip!] ... Blah, blah, blah. I'm sure it's different potty training twins vs. a singleton but I'm frustrated. Any advice? Thanks ladies."

All I did was put them in underwear. Diapers were gone and it was big girl pants. Every time they had an accident, I ran them to the bathroom. I didn't "force" them to sit on the potty, didn't set a timer, didn't make them sit there forever (although I wanted to   ) and gave them praise, lots and lots of praise.
You never know if your son is ready unless you try. Maybe is she sees you trying with him, it will push her.
I didn't think mine were ready at all. Good luck!