For I-134 for a sibling

[lawl]

I am inviting my parents are brother over. They're self sponsoring. In DS160, I said my brother's expenses will be paid for by my father. Am I gonna need an I-134 form to show that my father will sponsor my brother's travel expenses?

[peace999]

NO. I-134 is required only when the host in US is funding the trip.
In this case your dad will need to take his income proof to the interview.