I'm not so sure they look like hibiscus leaves, i've a hibiscus here and the leaves aren't that shape.

Hard to say what it is - could be a tree sapling, or possibly a Mallow...

Looks a bit like a couple in my garden some sort of tree?

the photo was taken a little too close to the plant, so focus not very sharp - can you post another? I'd hazard a guess at birch?

Could be a shrubby mallow, very similar.