a. We have to find the root cause of any problem these children have.
b. We have to find the root cause of any frustration these children feel.
Could these sentences be used if the speaker is not sure that the children do have any problems/frustration?
Do they imply that the children do indeed have problems/frustration?
I think they do. I think if we had 'might have' instead of 'have' then the speaker would be implying that he or she is not sure if there are problems/frustrations.
Many thanks.