Redditor emham06 noticed that Gabriel was introduced immediately after Annalise was seen holding Laurel’s baby boy and thinks there may be a familial connection between Laurel and Gabriel. Could he be Laurel’s half-brother? According to this poster, it seems unlikely because they are very close in age.

Her mother could have had a child and placed it for adoption, but that feels like a stretch because Laurel would have known about a sibling. But, he could be her half-brother via her father because who knows what he has been up to besides being a full-fledged criminal. If this is true, then it would be a major coincidence for him to arrive at the same school. Why would he suddenly appear from the shadows?

Or, he might have a purpose in mind since Laurel's father just went to prison. Perhaps he’s in town to confront Laurel for putting him away or to warn her about another threat coming her way. It's intriguing, but it doesn't explain the "her" mentioned by Frank. But, if it's true, then Gabriel cannot be trusted because everyone with Castillo DNA is shady.

Gabriel was only onscreen for a couple of minutes, but fans wasted no time pointing out that he looked similar to Wes Gibbins. And, harrisonwilk1 threw out a theory to fellow Redditors about Gabriel being Wes’ brother. It’s an iffy theory because he’s presumably younger than Wes and his mother Rose committed suicide when Wes was old enough to be aware of a sibling. If Gabriel was around, then why didn’t Wes ever mention having a younger brother?

There’s always the possible "given up for adoption" route, which would have made sense because Rose could have had another child after Wes. The pressure of having two kids, especially after the trauma she suffered with the Mahoney family, may have forced her to give the child up for adoption.

If he is Wes’ brother, then it's likely that Frank was calling Annalise because she knew Rose. And, maybe Gabriel found out about Wes’ death and is in town to exact revenge. Again, it’s pretty far-fetched, but it would be super entertaining.

So far, the most prevalent theory about Gabriel is that he’s Bonnie’s son. And, it is the most plausible one at this time. Bonnie allegedly gave birth to a stillborn baby as a teenager after experiencing repeated sexual abuse from several men. She was told by her abusive father that the baby died, but Nate found a file about Bonnie with a note saying “child alive?”

The timing fits well and it would be interesting to see Bonnie’s reaction to discovering that her baby didn’t die. The HTGAWM Reddit page took a poll about Gabriel’s parentage and an overwhelming majority voted for Bonnie. But, it seems like a far too easy answer for a show that’s known for unexpected plot twists.

Michaela was given up for adoption and virtually nothing has been revealed about her birth parents. The aforementioned poll had very few votes for Gabriel being Michaela’s biological brother, but it is an interesting concept. It would be totally unexpected because the common thought is that he is either Bonnie or Annalise’s child, even though the latter doesn’t make sense per the established timeline.

And, it could build a great story arc for Michaela, who has always seemed a bit confused about her life in general. It would be a way to connect her with her biological roots, but it doesn’t explain why Frank would be invested in a situation involving Michaela’s parents. However, Frank seems to know a little too much about everyone so it's not impossible.

There are probably dozens more wild theories about Gabriel on Reddit and it remains to be seen who is right. Will he somehow be Annalise’s child from an unmentioned pregnancy?

Could he be Laurel’s brother who wants to stir up more Castillo drama? Or, will the show throw a wildcard at us and make him Tegan’s son? Every Thursday night will bring us one step closer to the truth about this charming (and possibly evil) new character.