when parent thread sleep does sub threads also sleep?
There's no such thing as a "parent" thread really. One thread starts another, but then there's no particular relationship between them. For example, the starting thread can terminate without any of the new threads dying.
The starting thread sleeping definitely doesn't affect any other thread.
There is no concept of parent and child threads. One implication of this is that the child threads don't sleep when the parent thread sleeps.
Thread.Sleep(...)only suspends the current Thread.
check here: Thread.Sleep Method
so all other threads will keep working.