Wife and I filed separately in 2015 and 2016. Found out we should have done jointly. Difference of thousands in refund. Can we amend both years?

My wife and I married in 2015 but filed separately. We did the same in 2016. After talking to a friend about refunds and how we didn't expect much I was told to file jointly. This year while preparing my taxes we discovered we hadn't recieved the EIC for filing separately. The difference is over $3000 in refund. So I know we can amens our 2016 taxes. I want to know if we can amend our 2015 taxes as well.