Question: Osferth or Osferd or Osfrith, was described by Alfred the Great in his will as a "kinsman", he may have been a relative of Alfred's mother Osburh, or Osburga was the first wife of King Æthelwulf of which location?

Context paragraphs:
Lord Cardross: Lord Cardross is a title in the Peerage of Scotland, since 1695 a subsidiary title of the earldom of Buchan.  It was created in 1606 for John Erskine, 18th Earl of Mar, with remainder to his heirs male and assignees whatsoever and with the power to nominate his successor.  In 1617 he nominated his second son by his second wife, Henry Erskine, Master of Cardross, to be his successor in the lordship of Cardross.  The Earl of Mar died in 1634 and was succeeded in the earldom of Mar by his son by his first wife, John, and in the lordship of Cardross by his grandson David Erskine, the second Lord Cardross, the son of Henry, Master of Cardross, who had died in 1628.  The second Lord was a supporter of The Engagement and was barred from sitting in Parliament in 1649.  He was succeeded by his eldest son, the third Lord.  He emigrated to North America to escape religious persecution and established a colony in what is now Carolina.  His son, the fourth Lord, succeeded his kinsman in the earldom of Buchan in 1695.  However, it was not until 1698 that his claim was established by the Scottish Parliament.  For further history of the title, see Earl of Buchan.

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.

Æthelstan of Kent: Æthelstan (died c. 852), the eldest son of King Æthelwulf of Wessex, was the King of Kent from 839 under the authority of his father.  The late D, E and F versions of the "Anglo-Saxon Chronicle" describe Æthelstan as Æthelwulf's brother, but the A, B and C versions, and Æthelweard's "Chronicon", state that he was Æthelwulf's son.  Some historians have argued that it is more probable that he was a brother, including Eric John in 1966 and Ann Williams in 1978.  However, in 1991 Ann Williams described him as Æthelwulf's son, and this is now generally accepted by historians, including Frank Stenton, Barbara Yorke, and D. P. Kirby.

Æthelfrith of Mercia: Æthelfrith (fl.  880s – c. 904/915) was an ealdorman of southern Mercia, who flourished in the last two decades of the ninth century and the first decade of the tenth century.  His father is unknown.  He was married to Æthelgyth, daughter of Æthelwulf; Æthelwulf is unidentified, but a possible candidate is King Alfred the Great's brother-in-law, the ealdorman of the Gaini who died in 901.  Æthelfrith was father to four ealdormen: Æthelstan Half-King (East Anglia), Ælfstan (Mercia), Æthelwald (Kent), and Eadric (Hampshire).

Earl of Westmeath: Earl of Westmeath is a title in the Peerage of Ireland.  It was created in 1621 for Richard Nugent, Baron Delvin.  During the Tudor era the loyalty of the Nugent family was often in question, and Richard's father, the sixth Baron, died in prison while awaiting trial for treason.  Richard himself when young was suspected of plotting rebellion and imprisoned, but in later life was a staunch supporter of the Crown, which rewarded him richly for his loyalty.  The fifth Earl was a Major-General in the British Army.  The sixth Earl was sworn of the Irish Privy Council in 1758.  His son by his first wife, Richard Nugent, Lord Delvin, was killed in a duel at an early age.  Lord Westmeath was succeeded by his second son by his second wife, the seventh Earl.  He sat in the House of Lords as one of the original 28 Irish Representative Peers; he was also involved in a much-publicised divorce and action for criminal conversation.  He was succeeded by his son, the eighth Earl.  He was created Marquess of Westmeath in the Peerage of Ireland in 1822.  He had no surviving male issue and the marquessate became extinct on his death in 1871.  He was succeeded in the barony and earldom by his kinsman, Anthony Francis Nugent, the ninth Earl.  The eleventh Earl was an Irish Representative Peer from 1901 to 1933.

Judith of Flanders: Judith of Flanders (or Judith of France) ( 843 – c. 870) was queen consort of Wessex and countess consort of Flanders.  She was the eldest daughter of the West Frankish King and later Holy Roman Emperor Charles the Bald and his wife Ermentrude of Orléans.  Through her marriages to two Kings of Wessex, Æthelwulf and Æthelbald, she was twice a queen.  Her first two marriages were childless, but through her third marriage to Baldwin, she became the first Countess of Flanders and an ancestor of later Counts of Flanders.  One of her sons by Baldwin married Ælfthryth, a daughter of Æthelbald's brother, Alfred the Great.  She was also an ancestor of Matilda of Flanders, the consort of William the Conqueror, and thus of later monarchs of England.

Osburh: Osburh or Osburga was the first wife of King Æthelwulf of Wessex and mother of Alfred the Great.  Alfred's biographer, Asser, described her as "a most religious woman, noble in character and noble by birth".

Æthelberht, King of Wessex: Æthelberht (or Ethelbert; Old English: "Æþelberht" , meaning "magnificent noble") was the King of Kent from 858 and of Wessex from 860 until his death in 865.  He was the third son of Æthelwulf of Wessex and his first wife, Osburh.  In 855 he became under-king of Kent while his father, Æthelwulf, visited Rome.  His brother Æthelbald was left in charge of the West Saxons.  After his father's death in 858 he succeeded him as king of Kent and the other eastern parts of the kingdom.  When Æthelbald died childless in 860, the kingship of the West Saxons also passed to Æthelberht.

Æthelbald, King of Wessex: Æthelbald, King of Wessex (Old English: "Æþelbald" meaning "Noble and Bold") was the second of the five sons of King Æthelwulf of Wessex and Osburh.  He was king of Wessex from 858 to 860.

Osferth: Osferth or Osferd or Osfrith (fl.  c.885 to c.934) was described by Alfred the Great in his will as a "kinsman".  Osferth witnessed royal charters from 898 to 934, and in a charter of Edward the Elder he was described as a brother of the king.  He witnessed as an ealdorman between 926 and 934.  Simon Keynes and Michael Lapidge suggest that he may have been a relative of Alfred's mother Osburh, or a son of Oswald "filius regis" (king's son), who may in turn have been a son of Alfred's elder brother and predecessor as king, Æthelred I.  However, Janet Nelson argues that he was probably an illegitimate son of Alfred.

Supporting paragraphs: Osferth Osburh
Answer: Wessex