This question is not relevant in the least because Hrothgar and Grendel are both characters in the epic poemBeowulf:
Hrothgar is the king of the Danes (Scandinavia, or Denmark). The story mainly takes place in the Scandinavian mead hall named "Herot."
Grendel is the devilish monster that represents all that is evil. Grendel is the monster who encountered the sleeping warriors/drunkards of Herot in the middle of the night and ripped them to pieces only to then immediately consume them one by one and drink their blood. Beowulf killed Grendel with his bare hands because Grendel enchanted all the swordsmen's weapons, so they appeared blunt and could not penetrate his skin (after Beowulf's victory, he ripped off Grendel's arm and hanged it). And after Beowulf kills Grendel's vengeful mother in the moor, he beheads Grendel's dead body and brings it to the men of Herot.
So, to conclude this answer, you obviously have no grasp of the concept or any of this historical story's premise. In no place does it say anything about an amount of sons Hrothgar has.
It would be easier if you read it.
Grendel first encountered Hrothgar and his warriors during a feast in Heorot, their mead hall. Grendel attacked the warriors, killing many of them, which led to his ongoing feud with Hrothgar and the Danes.
Grendel harasses Hrothgar and the hall of Heorot for twelve years in the epic poem Beowulf.
Yes, Beowulf gives Grendel's head and the hilt of the magic giant's sword to Hrothgar, and Hrothgar gives Beowulf treasure and gold, new golden chain mail, horses and weapons. Hrothgar also gives the men who sailed with Beowulf treasure-gifts. These treasures are given to Beowulf after both the fight with Grendel and the fight with Grendel's mother. After he defeats Grendel's mother, Beowulf sails home with his men and his treasures.
Grendel terrorizes Hrothgar and his followers by attacking Heorot, the mead hall, every night for twelve years. He kills and eats many of Hrothgar's warriors, causing fear and despair among the people.
hrothgar
Hrothgar's companion who was killed by Grendel's mother was called Aeschere.
Grendel only ever attacks the hall, never any other building. Hrothgar and Wealhtheow retire to a bower (buhr) for the night. Beowulf similarly is not in the hall when Grendel's mother attacks.
Grendel doesn't touch Hrothgar's throne because it is protected by God. The throne represents Hrothgar's rule and power, and Grendel's inability to defile it signifies the presence of divine protection. This restraint shows the limits of Grendel's power and the influence of God in the story.
Hrothgar asks Beowulf to help him defeat the monster Grendel that has been terrorizing his kingdom. Beowulf responds to Hrothgar by vowing to protect his people and rid them of the monster. He laments about how Grendel has caused so much destruction and sorrow, and how he wishes to avenge the death of Hrothgar's people. There are several similarities between Hrothgar and Grendel and Grendel's mother. Both Hrothgar and Grendel are powerful warriors, and their actions are motivated by a desire for power and revenge. Both are also willing to take drastic measures to protect their people, such as Hrothgar building the great hall of Heorot, and Grendel and his mother attacking the hall. Both are also feared by the people of their kingdom, as they are seen as powerful and dangerous forces.
It is mentioned in the epic poem "Beowulf" that Grendel kills 30 geats in Hrothgar's hall, Heorot.
The monster Grendel is causing havoc in Hrothgar's kingdom in Beowulf. Grendel terrorizes the kingdom by attacking the warriors in Heorot, the mead hall.
Grendel imputes a horrible dream about tree trunks to Hrothgar. In it, The floor of the forest, he is standing in disappears, growing trees are fighting with one another. The flash of a sword is shown. The dream is recurring.