My ollder one did not finish with potty training until just after her third birthday, and the younger one, adopted almost a year ago at age 4, is still have accidents
(due to emotional issues). I do think 2 is on the young side.
I can tell you from experience (with the older one) that pressuring them really does backfire. The thing that finally got C to poop in the toilet was to let her run around naked at the time of day she normally pooped (in the evening). The first time, she said urgently "I need my diaper", and then she ran to the toilet. Only had to do that three days in a row. Good luck to you all!