Our children!?

Plot: 
The school has a new maths teacher, Mr. Bane, and he is only 15 years old. He has a twin sister and an older 1/2 sister. It is later revealed that Mr. Bane is from the future and is A.J's and Alexia's son, and his 1/2 sister is A.J's and Andrea's daughter.
They were there for many reasons like to stop WW3, end global warming, etc. But they were also their to make sure that their dad has a better education