13 /17 I mistyped the ages. correct ages are 13 and 17
Did you lived with the children's parents in 2008? Did the children lived with you in 2008?
You should sent to the IRS:
Copy of birth certificate for you, the children and your sister or brother.
If you lived in an appartment a copy of the lease if the children names are XXXXX XXXXX the lease.
Copy of the children's report card from school if the report card have the same address as your.
Any document that prove that the children lived in the same home as you in 2008.