That helps, but until they are 3 weeks old are they able to stay warm on their own.No, they're probably a couple weeks old, judging only by size (can we get a cat age expert in here?).
And a few hours.
Will they leave their young if human scent is there? We touched the blanket, and moved the cat on it.
I could tell you within a couple/few days their age if I knew more details.
No, moms don't leave them because of human scent.