Question: The father of Beorhtnoð æthling of Kent ruled Mercia between what years ?

Context paragraphs:
Baldred of Kent: Baldred was king of Kent, from 823 until 826 or 827.  Ceolwulf I, king of Mercia, had ruled Kent directly, but in 823 he was deposed by Beornwulf, and at about the same time moneyers at Canterbury started issuing coins in the name of Baldred, king of Kent.  It is uncertain whether he was independent or a Mercian under-king.  In 826 or 827 he was expelled by Æthelwulf, son of King Egbert of Wessex, and Kent was ruled directly by Wessex thereafter.

Æthelflæd: Æthelflæd, Lady of the Mercians ( 870 - 12 June 918) ruled Mercia in the English Midlands from 911 until her death.  She was the eldest daughter of Alfred the Great, king of the Anglo-Saxon kingdom of Wessex, and his wife Ealhswith.  Æthelflæd was born around 870 at the height of the Viking invasions of England.  By 878 most of England was under Danish Viking rule, East Anglia and Northumbria having been conquered and Mercia partitioned between the English and the Vikings, but in that year Alfred won a crucial victory at the Battle of Edington.  Soon afterwards the English-controlled western half of Mercia came under the rule of Æthelred, Lord of the Mercians, who accepted Alfred's overlordship.  Alfred adopted the title King of the English, claiming to rule all English people not living in areas under Viking control.  In the mid-880s, Alfred sealed the strategic alliance between the surviving English kingdoms by marrying Æthelflæd to Æthelred.

Coenwulf of Mercia: Coenwulf (also spelled Cenwulf, Kenulf, or Kenwulph) was King of Mercia from December 796 until his death in 821.  He was a descendant of a sibling of King Penda, who had ruled Mercia in the middle of the 7th century.  He succeeded Ecgfrith, the son of Offa; Ecgfrith only reigned for five months, and Coenwulf ascended to the throne in the same year that Offa died.  In the early years of Coenwulf's reign he had to deal with a revolt in Kent, which had been under Offa's control.  Eadberht Præn returned from exile in Francia to claim the Kentish throne, and Coenwulf was forced to wait for papal support before he could intervene.  When Pope Leo agreed to anathematize Eadberht, Coenwulf invaded and retook the kingdom; Eadberht was taken prisoner, was blinded, and had his hands cut off.  Coenwulf also appears to have lost control of the kingdom of East Anglia during the early part of his reign, as an independent coinage appears under King Eadwald.  Coenwulf's coinage reappears in 805, indicating that the kingdom was again under Mercian control.  Several campaigns of Coenwulf's against the Welsh are recorded, but only one conflict with Northumbria, in 801, though it is likely that Coenwulf continued to support the opponents of the Northumbrian king Eardwulf.

Æthelred of Mercia: Æthelred ( ; died after 704) was King of Mercia from 675 until 704.  He was the son of Penda of Mercia and came to the throne in 675, when his brother, Wulfhere of Mercia, died.  Within a year of his accession he invaded Kent, where his armies destroyed the city of Rochester.  In 679 he defeated his brother-in-law, Ecgfrith of Northumbria, at the Battle of the Trent: the battle was a major setback for the Northumbrians, and effectively ended their military involvement in English affairs south of the Humber.  It also permanently returned the kingdom of Lindsey to Mercia's possession.  However, Æthelred was unable to re-establish his predecessors' domination of southern Britain.

Mercian dialect: Mercian was a dialect spoken in the Anglo-Saxon kingdom of Mercia (roughly speaking the Midlands of England, an area in which four kingdoms had been united under one monarchy).  Together with Northumbrian, it was one of the two Anglian dialects.  The other two dialects of Old English were Kentish and West Saxon.  Each of those dialects was associated with an independent kingdom on the island.  Of these, all of Northumbria and most of Mercia were overrun by the Vikings during the 9th century.  Part of Mercia and all of Kent were successfully defended but were then integrated into Wessex.  Because of the centralisation of power and the Viking invasions, there is little or no written evidence for the development of non-Wessex dialects after Alfred's unification, until the Middle English period.

Beorhtweald Ealdorman of Kent: Beorhtweald Ealdorman of Kent was an English ruler of the 9th Century AD.  His father was Burgred of Mercia, his mother: Æthelswith, and his brother,: Beorhtnoð æthling of Kent.

Burgred of Mercia: Burgred (also Burhred or Burghred) was an Anglo-Saxon king of Mercia from 852 to 874.

Æthelwulf: Æthelwulf (Old English for "Noble Wolf"; died 13 January 858) was King of Wessex from 839 to 858.  In 825, his father, King Egbert, defeated King Beornwulf of Mercia, ending a long Mercian dominance over Anglo-Saxon England south of the Humber.  Egbert sent Æthelwulf with an army to Kent, where he expelled the Mercian sub-king and was himself appointed sub-king.  After 830, Egbert maintained good relations with Mercia, and this was continued by Æthelwulf when he became king in 839, the first son to succeed his father as West Saxon king since 641.

Beorhtnoð æthling of Kent: Beorhtnoð æthling of Kent was an English ruler of the 9-10th century AD.  His father was Burgred of Mercia; his mother, Æthelswith, and his brother, Beorhtweald Ealdorman of Kent.

Beorhtwulf of Mercia: Beorhtwulf (] , meaning "bright wolf"; also spelled "Berhtwulf"; died 852) was King of Mercia, a kingdom of Anglo-Saxon England, from 839 or 840 to 852.  His ancestry is unknown, though he may have been connected to Beornwulf, who ruled Mercia in the 820s.  Almost no coins were issued by Beorhtwulf's predecessor, Wiglaf, but a Mercian coinage was restarted by Beorhtwulf early in his reign, initially with strong similarities to the coins of Æthelwulf of Wessex, and later with independent designs.  The Vikings attacked within a year or two of Beorhtwulf's accession: the province of Lindsey was raided in 841, and London, a key centre of Mercian commerce, was attacked the following year.  Another Viking assault on London in 851 "put Beorhtwulf to flight", according to the "Anglo-Saxon Chronicle"; the Vikings were subsequently defeated by Æthelwulf.  This raid may have had a significant economic impact on Mercia, as London coinage is much reduced after 851.

Supporting paragraphs: Beorhtnoð æthling of Kent Burgred of Mercia
Answer: 852 to 874