Kyle Hale,
I am not sure why you are referring to get "next row's Start date" with Windowing function but to get the "next row's End date":
SELECT [Id]
,[NId]
,[Name]
,[HomeTown]
,[MaritalStatus]
,[NumberOfChildren]
,[SCDStartDate]
,COALESCE(LEAD([SCDStartDate]) OVER (PARTITION BY [NId],[Name],[HomeTown] ORDER BY [NId]), '99991231') "SCDEndDate"
,CASE WHEN LEAD([SCDStartDate]) OVER (PARTITION BY [NId],[Name],[HomeTown] ORDER BY [NId]) IS NULL THEN 1 ELSE 0 END "IsLatest"
FROM dbo.Customer C
