How is it known that William's wife is Hannah? Doing some quick searches, I find a few marriage records that could match. Given that William II is born ~1725, they have to be in the States and married before then.
As far as marriages go in the states, I found one that makes sense, a marriage of William Frazier to a Hannah Clemons on 3 Feb 1715 at Christ Church and Saint Peters in Philadelphia, Pennsylvania. However, this seems strange to me given that they are a Virginia family. Nonetheless, Christ Church is relatively close to Henrico. Indeed, William could have landed in New York or somewhere else northward and then proceed to move southwards, stopping in Philadelphia and finding a wife. This is speculation, but could explain that record.
Looking into marriages in Scotland, I quickly found two. A William Frasr. to unknown on 9 Sept 1684 in Ardclach, Nairn, Scotland. The second is a William Frazer to unknown on 2 Sept 1677 in Carnbee, Fife, Scotland. Either of these could be possible, but as far as Scottish marriages go, that's it for Wm. Fraziers', unless he got married in London, which is more unlikely.
Thus, if the Nairn marriage is truly William, then could it be assumed that he is of Clan Fraser and if the Fife marriage is true, is he Clan Fraser of Lovat? And if he was truly passing through Philadelphia and married Hannah Clemons, we certainly have more work to do. Any information about the Henrico Frazier's descent from Scotland is greatly appreciated!
All the best,
Don