Glóin is the father of Gimli in The Lord of the Rings.
Glóin is one of the thirteen Dwarves who accompany Thorin Oakenshield in The Hobbit. He is a member of the royal House of Durin and later becomes an important representative of the Dwarves. His son Gimli joins the Fellowship of the Ring and becomes one of the principal companions of Aragorn, Legolas, and Frodo.
The relationship is easy to miss because Glóin is much more prominent in The Hobbit than in The Lord of the Rings. In The Fellowship of the Ring, Glóin attends the Council of Elrond at Rivendell and helps explain the events involving Bilbo and the wider Dwarven world.
Glóin is sometimes confused with other Dwarves connected to Thorin’s company. Thorin is the leader, Balin is an elder companion, and Dáin Ironfoot is Thorin’s cousin and successor as King under the Mountain. None of those three is Gimli’s father.