Yet, somehow, Gimli was unaware of Moria's fall until he discovered Balin's tomb. All he knew was that Balin's mission was initially successful, which is why he suggested the Fellowship should travel through the Mines of Moria: He wanted to visit family.
Desperate to learn the fate of the Dwarves, Gimli said, “I will go and look on the halls of Durin, whatever may wait there.” This suggests that Gimli was not entirely naive about what may have happened. He did not even actively encourage the Fellowship to travel through Moria, until it became their last resort.
Combining the poor communication between Erebor and Moria with the Dwarves' extended lifespans, Gimli might not have known about the fall of Moria simply because Erebor had not grown too worried about the lack of information yet.
His father joined Thorin and Company in their quest to reclaim the Kingdom under the Mountain, but Gimli was forbidden because he was too young: only 62 at the time. The Dwarves were successful in their Quest and Gimli and his father were among the Dwarves who returned to Erebor.
The Dwarves dug too greedily and too deep for mithril, and disturbed a demon of great power: a Balrog, which destroyed their kingdom. By the end of the Third Age, Moria had long been abandoned by the Dwarves, and was a place of evil repute.
Though Gimli has no children, he is not the last Dwarf of Middle-earth. After the fall of Sauron, his people continued to thrive in the Lonely Mountain. Gimli made his home in Rohan, in the Glittering Caves of Aglarond, and many of his kinsfolk came with him.
After the battle, Thráin wanted to enter and reclaim Moria, the ancestral home of Durin's folk. However, due to their losses, the other Houses not willing to participate, and since Dáin had seen Durin's Bane beyond the East-gate, Thráin refrained from entering.
From TA 2989 to TA 2994, the re-colonization of Moria was an attempted expedition led by Balin to re-take the ancient Dwarven Kingdom of Khazad-dûm. An initial effort was successful in reclaiming some of Moria from the Orcs.
Gimli was born in the Ered Luin in the Third Age, son of Glóin. Gimli had wanted to accompany his father on the quest to reclaim Erebor, but at age 62 he was deemed too young. He was a remote descendant of Durin the Deathless, chief of the Seven Fathers of the Dwarves and ancestor of the Longbeards.
Gandalf didn't know that the Mines of Moria had fallen. He mentions he had been through Moria before, but it was before it had been resettled, which means it would not have had the chance to be overrun yet. All that was known about the mines was that the dwarves had gone silent.
When The Fellowship is taken to Galadriel, she and Boromir have a telepathic conversation which immediately causes Boromir to burst into tears. She senses his desires for the Ring but tells him not to give in because even now, there is hope.
Therefore, the only explanation as to why Gandalf doesn't reveal the Balrog's presence to the others earlier in the films, is that it is a plot device used by the writers and the creative team in order to increase the dramatic tension of Frodo's decision.
Balin was distantly related to him, and a descendant of the noble House of Durin. He later went to re-establish the Dwarf presence in Moria, but within five years it was overcome once more by Orcs, and he was killed there along with the rest of his companions.
In the end Tolkien stated that there were probably "at most" seven Balrogs: In the margin my father wrote: 'There should not be supposed more than say 3 or at most 7 ever existed. '
Why doesn't Gimli know the password to the Mines of Moria? Gimli didn't know the password to the door because that knowledge was lost. It was too long ago when dwarves had lived there. Elves built the door, back when they were friends with the Dwarves, thousands of years beforehand.
Thorin I (Third Age 2035 – 2289, died aged 254) was the King of Durin's Folk for 99 years, succeeding his father, Thráin I, on his death in T.A. 2190. Thorin was the heir of Durin the Deathless being the great-grandson of Durin VI.
Early life. Born in TA 2879, Gimli was the son of Glóin and a nephew of Óin, both former companions of Bilbo Baggins. He was a descendant of Durin the Deathless, father of the first house of the Dwarven people. Gimli was descended from, but was not a member of the royal line.
Gimli is the son of Glóin who is introduced in The Hobbit as a member of Thorin Oakenshield's company, also being one of his four third cousins. Thorin himself is a direct descendant of Durin I, even becoming the King of Durin's Folk in his lifetime.
Did All The Dwarves Die In Moria? While six have perished, seven dwarves from The Hobbit are still alive when The Lord of the Rings begins, only one of which actually appears in the movies.
Thorin's nephews Fíli and Kíli are killed, and Thorin is mortally injured; he dies shortly afterwards. The title of King under the Mountain passes to Dáin.
The Orcs of the Mountains though permanently depleted, reclaimed Moria though returning to the service of the Dark Lord Sauron. Sauron's turncoat servant, the fallen Wizard Saruman also stirred up the Orcs tribes in the Mountains, gathering some of the forces he used against the kingdom of Rohan from there.
