Robett is the brother of Galbart Glover, the Lord of Deepwood Motte. He succeeded him after Galbart's death in the War of the Five Kings.
"Yes, my family served House Stark for centuries. We wept when we heard of your father's death. When my brother was Lord of this castle he answered Robb's call and hailed him King in the North! And where was "King" Robb when the Ironborn attacked this castle? When they threw my wife and children in prison and brutalized and killed our subjects? Taking up with a foreign whore... getting himself and those who followed him killed. I served House Stark once, but House Stark is dead." ―Lord Robett Glover responds to Jon Snow and Sansa Stark's plea for help.
Jon Snow, Sansa Stark, and Davos Seaworth secretly meet with Robett to try and gain his support against House Bolton. He refuses to help, as they have only secured the loyalty of House Mormont, and citing that Jon Snow has joined forces with wildlings, whereas the Boltons helped him take Deepwood Motte back from the Ironborn who had captured it and terrorised Robett's family and subjects. Robb Stark, to whom House Glover was sworn, gave no such help (though in all irony, this was Robb's original intention, but he was persuaded otherwise by Roose Bolton). Despite their protestations, Robett refuses to declare for them, and sends them away empty-handed.
Robett, along with other Northern lords, travels to Winterfell following its capture by Jon, where he and the others are berated by Lady Lyanna Mormont, who did offer help to the Stark cause. Robett is the second lord, after Wyman Manderly, to declare Jon King in the North. He apologises for not participating in the battle, and pledges his allegiance to House Stark and Jon Snow.
Robett Glover refused to grant Deepwood Motte's support to Jon Snow and Sansa Stark's fight against Ramsay Bolton.