Maybe we can go back to using contemporary sources for documentation ;)
In one format or another, most of us English-speakers are probably already using Goss's translation of Munch's edition of the Chronicle of Man and the Sudreys, printed by The Manx Society in 1874.
http://www.isle-of-man.com/manxnotebook/manxsoc/msvol22/index.htm#c...
This edition includes a translation of a pedigree chart prepared by Munch. There is no indication there of the Skanke claim.
http://www.isle-of-man.com/manxnotebook/manxsoc/msvol22/adx_d55.htm
In the entry for 1249 the Chronicle says "Harold, the son of Godred Don, usurping the name and dignity of king in Man, drove out nearly all the chiefs of Harold, Olave's son, and in their stead made the fugitives who had joined him chiefs and nobles."
In 1250 the Chronicle says "Harold son of Godred Don was summoned, amid went to time Court of the Lord King of Norway; for the king was displeased with his having usurped a kingdom to which he had no title, and intended not to allow his return to the Sodor Islands." (Then describes Manx resistance to having "John son of Dugald" as king because they wanted Magnus son of Olave.)
Skipping forward, in 1252 Magnus son of Olave returns to Man and is hailed as king. In 1254 the Norwegian king Haco appoints Magus as king. In 1263 the Norwegian king dies. In 1265 Magnus dies. In 1266 the "kingdom of Man and the Isles" was transferred to the king of Scotland. In 1275 the Scottish fleet was defeated by the Manx.
http://www.isle-of-man.com/manxnotebook/manxsoc/msvol22/p101.htm
That's it. No mention of the Skanke family and their supposed connection to the Manx kings.
Instead, Note 53 to the edition (probably by Goss but perhaps by Munch) says:
"According to the Chronicle of Lanercost the expedition here mentioned was caused by a new rebellion of the Manxmen, who had taken Godred, the son of Magnus, for their king. We give the entry at length, as a supplement to our Chronicle Hoc anno (1275) septima die mensis Octobris, applicuit navigium regis Scotiae in party de Reynaldsway. Statim dominus Johannes de Vesci 1 et optimates regis cam exercitibus suis in insuicem Sti Michaeiis ascendebant, Mannensibus paratis ad proelium, cum Godredo filio Magni, quem paullo ante regem constituerant sibi. .Magnates vero et capitanei regis Scotiae legationem pacis ad Godredum et populum Manniae transmiserunt, pcecem dei et regis Scotiae eidem afferentes, si a stultissima praesumtione sua desisterent, et se vitro regi et optimatibus suis dederent. Godredo autem et perversis quibusdcem consiliceriis suis legcetioni pacis non consentientibus, sequenti die ante solis ortum, cam adhuc tenebrae esset super terram, et corda stultorum hominum obtenebrata essent, conflictus factus est, et miseri Mannenses terga vertentes miserabiliter corruerunt.2 If Godred, as it would seem, was among the slain, the male line of the Godredian dynasty expired in his person. The female line seems to have survived for one generation more, for in the year 1293 one Affreca, related to the last king, Magnus, and pretending to be his legal heir, claimed the Isle of Man, as we learn from a letter issued June 15, 1293, by King Edward I. to John Baliol, then King of Scotland, citing him as a vassal of the English crown, to appear before his court, and receive judgment in the same case.3 It must be added that the Island had been lately made over by Edward to King John (see letter dated January 5, 1293, Rymer, Faed. i. 9. p. 785), the inhabitants having three years before (Rymer, 1. c. p. 740) of their own free will put themselves under the protection of King Edward.4 This Affreca was no doubt a grand-daughter of her namesake, the daughter of King Godred, mentioned heretofore (p. 80, ad. ann. 1204) on her marriage with John de Courcy, and named after his grandmother, as she again, in her turn, was named after her grandmother, Aifreca of Galloway, King Olaf’s Queen (vide p. 60, ad ann. 1102). What was the issue of the lawsuit we do not know; nor do we think it necessary to dwell on the entries in our Chronicle for the years 1313 and 1316, as being sufficiently explicit to want any explanation.5"
The Latin here is translated in Footnote 2: [Upon the 7th of October (1275), the fleet of the King of Scotland put into the port of Ronaldsway. John de Vesci and the king’s nobles immediately landed their forces on the island of St. Michael, the people of Alan being prepared for the encounter, along with Godred, the son of Magnus, whom they had made their king but a short time previously. The chiefs and officers of the King of Scotland, however, sent an embassy of peace to Godred and the people of Man, offering to them the peace of God and of the King of Scotland, on condition of their laying aside their absurd presumption, and of giving themselves up to the king and his nobles. As Godred, however, and some of his perverse counsellors did not agree to the terms of the embassy, on the following day, before sunrise, whilst darkness still covered the earth, and thee hearts of foolish men were darkened, an engagement took place, and the unfortunate people of Man running away, fell miserably.]
http://www.isle-of-man.com/manxnotebook/manxsoc/msvol22/note_53.htm