The two groups hail from Northumberland, and Y-DNA indicates that they are genetically different to each other.
1 The 'N group' originated with John b1634-40 who lived at Newton near Alwinton in Northumberland. He fathered four children b1680-1685 and possibly another b1720. George b1680 John b~1682 Mary b~1684 William b~1685, c1689 Robert c1720 Testamentary evidence indicates that the considerable wealth of this family was largely kept intact. While this group currently has 1,100 named descendants, it should have many more, suggesting further research is warranted.
2 The 'Z group' originated with John (b1793 in Wooler) and Anna in Northumberland with both interred in St Michael’s churchyard in Alnwick. The memorial inscription there shows that all those buried before June 1847 were inscribed as Whillans on the gravestone, while those after were Weallans; only three months separated the last Whillans and the first Weallans. The surname had changed quickly to Wealleans. John & Anna had at least eight children. John b1793 Elizabeth b1795 Michael b1797 James b1799 Robert b1801 Anna b1803 William b1806 Joseph b1810 This group has 1,120 named descendants, one of whom has an almost identical Y-DNA to the author, a descendant of James Whillans b1688.