Issues With Spaces In A Field

The name field in our database stores the name in the below format:

Shields~Joseph A
Simmons~Russell G
Resig~Benjamin R
Lindsey Jr.~Harold H
Jordan~Adante D
Kerr~Luke D
Adkins~Guillermo B
Conrad~Brian P

I am trying to separate the last name and first name into 2 fields. I do not want the middle initial or Jr. in the field. I am using the statement below but i am running into an issue with names that have Jr. on them because there is an extra space in the name.

SELECT SubString([Name],CHARINDEX('~',[Name])+1, (CHARINDEX(' ',[Name])-1) - (CHARINDEX('~', [Name])-1)) as FirstName,
Left(Name,CHARINDEX('~',Name)-1) as LastName
FROM Employee
WHERE StrtDate >'7/1/06' and StrtDate < '8/31/06' and Status = 'A' and BirthDate < GetDate() - 7665

Any help would be appreciated.