keying tree

Hi!

Is it possibly to get this property of keys: H is hash function and k1,
k2 ...kn is symmetric keys of size 128 bit. Assume I binary tree
structure where k1, and k2 is in the lowest layer, and k3 is the parent
of k1, and k2. Now the question: is this possibly H(k1)=k3 and
H(k2)=k3, but k1 is not equal to k2, if possibly how much information
about k3 do you get from k1, k2?

Regards
Ulf Reiman