HI .. yeah I'd originally just copied it off Ancestry - it appears they were known by both names .. see http://www.oxforddnb.com/view/10.1093/ref:odnb/9780198614128.001.0001/odnb-9780198614128-e-27704 . If you look at my page for him I have a note for this, but indeed the "William Steuart" name might have been more common.