What Happened to Andrew and Tristan?

Andrew's parents had another boy Tristan two years after Andrew was born and the two brothers have been inseparable their whole lives. By age 11, he was in his words, man of the house looking after his younger brother and now sister. The town in England they live in was called Luton and it is still I think it's usually pronounced by English people Luton. Robert: "I didn't think we would get an accent this episode but I'm glad we did"