Jose Fernandez Married His High School Sweetheart in 2012

We now know why Jose Fernandez's marital status was listed as divorced in his death certificate -- he wasn't even old enough to drink when he got married back in 2012.

TMZ Sports did some digging and according to the marriage license we've obtained ... Jose and Alejandra Baleato Marichal got married in December 2012 in Tampa, Fla. They were both 20 when they tied the knot.

According to court records ... the marriage lasted only 18 months.

We broke the story ... Jose's death certificate listed him as having been divorced. We knew he had a pregnant girlfriend at the time of his tragic boating accident, but knew nothing about an earlier marriage.