Lothar is married to Leonella Lefford and they have four daughters, Tysane, Walda, Emberlei, and Leana. He's the older brother of Jammos, Whalen, Morya, and Tyta Frey.
In the TV adaptation Game of Thrones he has been portrayed by Tom Brooke in the third season. In the sixth season he was portrayed by Daniel Tuite.
After King Robb Stark breaks the marriage pact to marry a Frey, the angered Freys leave his cause in protest. However, Lame Lothar later comes to Riverrun with his half-brother Walder Rivers for Lord Hoster Tully's funeral. He negotiates with Robb, agreeing that the Freys will return to supporting Robb and join him in his campaign to retake the North from House Greyjoy if Robb's uncle Edmure Tully, the new Lord of Riverrun, marries Roslin Frey, one of his half-sisters. This is agreed and Robb, his mother Catelyn, and Edmure start north for the Twins. However the wedding is a trap, becoming known as the Red Wedding. Robb Stark, Catelyn Stark and most of their forces are killed, with Edmure Tully and many other Northern and Riverlands nobles being taken captive. Lame Lothar is one of the main architects of the Red Wedding, plotting it out with Lord Roose Bolton, Lord Tywin Lannister, and Ser Rolph Spicer. He rigs the three tents much of Robb's army are feasting in to collapse. They have been soaked in oil and are set alight by flaming arrows, burning the men inside. He also puts crossbowmen in the gallery with the musicians. It is Lothar's idea to use the song "The Rains of Castamere" as a signal for the massacre to begin. Lothar assigns his half-brother Merrett Frey to make Greatjon Umber too drunk to fight. However Merrett fails, the Greatjon is too strong and is still able to fight. It takes eight men to put him in chains and even then two are wounded, one killed, and Ser Leslyn Haigh has half his ear bitten off.
Merrett Frey thinks that Lothar may be more dangerous then Edwyn Frey and Black Walder Frey, two of Walder Frey's great-grandsons high in the line of succession, Lothar quipping these brothers hate each other more then they do the other Freys.
- In the HBO series Lame Lothar begins the massacre when he stabs Talisa, Robb Stark's pregnant wife, causing her to bleed to death and killing her unborn child. Before the massacre begins he can be seen laughing with Talisa, using is usual polite and friendly behavior in the TV series as well.
- He is later killed by Arya Stark as vengeance for the Red Wedding and baked intő a pie.