Early reports have then in the US since 2007 which would put these kids at around 13 & 14 when they came over. Most of what we have seen so far would be things they could have gotten from watching TV and from the Internet. I see nothing that shows a lot of training.
The one older boy was into boxing, in fact took off school to go into boxing.
Pro's would have made the Canadian border in the time authorities are looking for them.
The older Brother Tamerlan Tsarnaev and the one still being sought is Dzhokhar Tsarnaev. The younger went to a local High School and was known as Johar.