I should know the answer to this, but am having a brain freeze. 3 siblings own a residence together. There is no mortgage on the property at this time. Sibling #1 is taking out a mortgage on the property to buy-out the other two. I believe this is not HMDA reportable, as #1 already has ownership in the property, i.e. not a purchase.
Any thoughts?

I would say that it is HMDA reportable. The explanation for Home Purchase loans (page A-8 of GIR) states that "this code applies to loans and applications made ofor he purpoe of purchaisng a residential dwelling for one to four families, if the loans is to be secured by the dwelling being purchased or by another dwelling."

No where in that explanation is there a caveat stating unless the borrower already had some ownership interest in the home. So, my reasoning would be that if the money is being used to buy out the other partners it is being used to purchase the home and it is therefore HMDA reportable.

I concur, and ROR will also apply if the home is currently Sibling #1's primary residence (226.2(a)(24)).