Trapping for more variables on Splitting out name filed

Currently using the below code, but found some places it's not working.  Examples that it returns nulls are:

John Smith and ASSC
John J. De La Smith

Create Function FirstName
(
	@name varchar(50)
)
RETURNS varchar(50)
AS
BEGIN

SET @name = REPLACE(REPLACE(REPLACE(@name, '  ', ' '), '.', '~'), ' ', '.')

SET @name = Case When parsename(@name, 1) in ('JR')
            Then ISNULL(parsename(@name, 4) + ' ', '') + parsename(@name, 3)
            Else ISNULL(parsename(@name, 4) + ' ', '') + ISNULL(parsename(@name, 3) + ' ', '') + parsename(@name, 2) End

RETURN REPLACE(@name, '~', '.')
END
GO    
Create Function LastName
(
	@name varchar(50)
)
RETURNS varchar(50)
AS
BEGIN

SET @name = REPLACE(REPLACE(REPLACE(@name, '  ', ' '),'.','~'), ' ', '.')

SET @name = Case When parsename(@name, 1) in ('JR')
            Then parsename(@name, 2) + ' ' + parsename(@name, 1)
            Else parsename(@name, 1) End

RETURN REPLACE(@name,'~','.')
END
GO

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