Rep. Ilhan Omar‘s ex-husband — who has long been rumored to be her brother — was apparently nowhere to be found when it came time to end their marriage … leaving a judge to finalize the divorce without him … TMZ has learned.

According to court documents, obtained by TMZ, Omar was granted a divorce from Ahmed Nur Said Elmi on December 4, 2017, in Minnesota’s Hennepin County District Court … after the judge found he failed to show up or respond to the proceedings.

The documents show Omar and Elmi married in February 2009 in Eden Prairie, Minnesota … but had been separated for more than three years by the time their divorce was finalized.

Here’s where things get interesting … the filing states Omar gave birth to a daughter in June 2012 while still legally married to Elmi, but identifies Ahmed Hirsi — another man with whom she had a relationship — as the child’s father.

The docs also note Elmi had not signed a declaration of non-paternity … with a handwritten addition explaining Omar had no contact with him since before the child was conceived.

As for Elmi’s whereabouts … his address was listed as unknown in the docs, and the court granted Omar a divorce after he failed to respond to notices published three times in August and September 2017.

The judge also awarded Omar her Toyota Camry, retirement accounts, and personal bank accounts … while neither party was ordered to pay spousal support.

The documents are drawing fresh attention amid allegations Omar married Elmi, a British citizen, to help him obtain immigration status … with critics claiming the two are actually siblings. However, that relationship has never been established.

As TMZ previously reported … Omar was asked earlier this month whether Elmi was her brother, responding, “Not to my knowledge” — and she has repeatedly denied wrongdoing.

And in another twist … Elmi identified himself as a gay man in an academic paper published in August, adding to the public scrutiny surrounding their former marriage.