​Game of Thrones has no new episodes in sight, so there's not much to do but theorize, speculate, and wait. For this reason, some theories might not be backed up so well. But regardless, in a new Instagram post, ​Cersei Lannister actress Lena Headey hinted at a ​theory about Tyrion's lineage that's been on our minds for awhile.  

On Friday, Lena posted a photo of herself with on-screen siblings Peter Dinklage (Tyrion Lannister) and ​Nikolaj Coster-Waldau (Jaime Lannister). She captioned the post: "Now this is more like it. Congratulations to my brothers (literally) from other mothers. I'm a lucky lucky sista to these Mistas."

Now, the post doesn't seem too special, and one could say Lena is simply congratulating her costars for their Emmy nominations. But for fans who have already been considering Tyrion having a different father, Lena seems to be confirming that.

But as we said, this theory isn't super airtight, as she even wrote "other mothers," not fathers. Even still, the idea seemed pretty convincing even before Lena's post.

In the books, Tyrion's mother Joanna Lannister was rumored to have had a relationship with The Mad King, Aegon Targaryen, around nine months before Tyrion's birth. In addition, ​Tywin's final words to Tyrion were: "You're no son of mine," possibly implying he knew Tyrion was a bastard.

Finally, Tyrion and Daenerys seemed to have an instant connection, and they quickly trusted and respected each other. Tyrion also has confidence when interacting with the dragons, and even recalled his obsession with the creatures as a young boy. Maybe he does have Targaryen blood after all.

There's no real way to know until ​Season 8 comes out in 2019.