You can try Teagan but unless she is willing to co-operate then it's no point.
Mason had shown interest to sit on the toilet before I had Angus (he was 22 mths when Angus was born) but he didn't do anything on it.
He regressed with his speech after his brother was born and he also refused to sit on the toilet or potty as well.
ISKWYM about not wanting to have 2 in nappies but in the end it is really up to them.