Alexander Oniciuc age five months on his potty. Alexander Oniciuc has been potty trained before the age of five months old his sister now age three was also a fast learner and was potty trained before she was six months old. See SWNS story SWPOTTY; A mum is proud to show off her miraculous son who successfully potty-trained himself – by the age of just FIVE MONTHS. Despite not being able to walk unaided, clever little Alexander Oniciuc (corr) warns mum Raluca or dad Finn whenever he needs to go by shouting – and hasn’t had an ‘accident’ in EIGHT WEEKS. Incredibly, little Alex, who was born last October, has beaten his older sister Izabella, now three, who learned to go on her own aged SIX months.