A more sensible suggestion is that, assuming Magnuss right to Caithness was inherited from his mother, she was related to the last Earl John, who died in 1232, and whose rights would have been divided between his two heiresses.] .Balfour Pauls Scots Peerage states that William King of Scotland granted lands of "Purin, Ogguluin and Kinminethen" [Powrie, Ogilvie and Kilmundie] all in Forfarshire to "Gilbert son of the Earl of Angus" by charter dated to [1172/77], and that "from him are descended the Ogilvies of that Ilk, Airlie with its cadets, and Inverquharity" ([1175/85]-1239).After the introduction of the feudal system into Scotland in the 12th century, the earldoms were descendible to heirs general was one of the seven original provinces of Scotland, covering about the same territory as the modern Scottish county of Forfar.Its ruler was one of the six Mormaers who were described as "comes" in the [1114/15] charter of Scone. The 10th century Pictish Chronicle Cronica de Origine Antiquorum Pictorum records the death of "Dubucan filius Indrechtaig mormair Oengusa, Adalstan filius Advar rig Saxan, et Eochaid filius Alpini" .The separate primary source references to an individual named Magnus indicate that this suggestion is probably incorrect.From a chronological point of view, Magnuss estimated birth date range as shown above suggests that he was either the son of Gillbride Earl of Angus by a second marriage or that he was the son of Earl Gilchrist.A charter dated 1351 which confirmed the donation of "terram de Kenny" to Aberbrothoc by "Walterum filium Turpini" quotes a document witnessed by "Domino Magno filio Comitis Domino Anegus filio Comitis".He was apparently installed as Earl of (part) Caithness.
It does not cite the source on which this statement is based and, as discussed further above under the possible second wife of Earl Gilbride, the hypothesis appears to be entirely speculative.
There appears to be no surviving contemporary evidence concerning the grant of the earldom.
However, Balfour Paul refers to a charter "noted in an old Inventory of Oliphant writs, made about 1594, and preserved in the General Register House" which states that King Alexander II granted "the erledom of South Kaythnes" to "Magnus sone to Gylcryst sum tyme erle of Angus".
No primary source is cited in support of these statements and it is possible that this marriage, and the supposed parentage of the bride, are entirely speculative, in an attempt to explain the transmission of the half of the earldom of Caithness to Earl Magnus (see below).
Skene says that "the probability is that the half of Caithness which belonged to the Angus family was that half possessed by the earls of the line of Erlend, and was given by King Alexander with the title of Earl to Magnus, as the son of one of Earl Harald "Ungi"s sisters" and that "the Norwegian name of Magnus indicates that [Earl Magnus] had a Norwegian mother".