@branschwe there are plenty of reasons to be eligible for the exclusion that forces your to sell in less than 24 months prior to ownership. but I can see no exclusions that permit you to be eligible for the exclusion based on some theory of purchasing when your name is not on the deed.
https://www.irs.gov/pub/irs-pdf/p523.pdf
Intent isn't the proof, documentation of purchasing the property is. and hoping you do not get audited isn't a strategy. see a tax lawyer, pay them and get it in writing.
there is no reason you could not have been on the deed from the beginning with your sibling on the mortgage. Or that written agreement to share utilities and mortgage could have included language to share ownership, but it didn't. that is where the story breaks down. you could spin any yarn you want but it could have easily been resolved in 2012 or through that written agreement. I do not see you have a leg to stand on to claim 24 months of ownership.
