James, Thomas and Olivia Prentice will be familiar to BBC viewers as they featured in a programme about the human body.
Now they have reached another milestone as the triplets, from Killingbeck, Leeds, started school at Manston St James School Primary Academy in Cross Gates this week.
Their mum Diane Oderlap said: “It’s been quite an emotional day.”
Diane and her partner Michael Prentice were stunned to be told at their 12-week scan that she was carrying three babies.
“I started laughing and crying at the same time,” the 42-year-old said. “They’re my first, so I left it until later in life but then I got three surprises at once.”
During her pregnancy she saw a call for mums of naturally-conceived triplets to volunteer for the BBC Inside the Human Body programme and was chosen to appear.
From being five months pregnant until the triplets were three months old, the family were filmed around eight times.
There was even a crew on standby when she went into labour, which she did early at 31 weeks, and their delivery by emergency caesarean at LGI was featured on the 2011 show.
The babies were in hospital for four weeks, but are now healthy four-year-olds with distinct personalities.
Diane said: “We didn’t get paid for it, we did it for the memories. It was such a special pregnancy and I wanted it documented.”
Thanks to increased availability of fertility treatment, the chances of having more than one baby during a pregnancy have increased by almost 50 per cent since the early 1980s.
However rates of multiple births have more recently dropped as regulations have been tightened up.
The Prentice triplets were conceived naturally, which is more unusual, and came from three separate eggs.
Their mum said they have quite different characters, with the eldest James being confident and boisterous and Thomas more reserved and sensitive. Olivia, the youngest, is bossy, girly and very protective of her brothers.