Need VBA Macro to Copy and paste column data in blank rows and repeat through spreadsheet

Hi All,

Im a bit of a n00b with these Macros and have been trying to modify some VBA code I used for a different but similar task without success. What I want to do is ensure that there are no blank cells in the the first 2 columns of my spreadsheet.

The data is stored like this

AA : 12 : 34 : 45
: : : 46
: : : 47
BB : 23 : 34 : 48
: : : 49
CC : 45 : 34 : 50
DD: 67 : 34 : 51
: : : 52
: : :53
EE: 91 : 34 :54

And id like the Macro to run through the sheet a copy columns 1 and 2 and paste them into proceeding rows until they hit the next set of data, then copy those cells and paste until they hit the next and so on, so the sheet looks like this

AA : 12 : 34 : 45
AA : 12 : : 46
AA : 12 : : 47
BB : 23 : 34 : 48
BB : 23 : : 49
CC : 45 : 34: 50
DD: 67 : 34 : 51
DD: 67 : : 52
DD: 67: :53
EE: 91 : :54

Sorry for the shitty drawing but let me know if you have any ideas. This is what I tried to no avail

Sub AddBlankLines()

    Dim Col As Variant
    Dim BlankRows As Long
    Dim LastRow As Long
    Dim R As Long
    Dim StartRow As Long

        Col = "A"
        StartRow = 1
        BlankRows = 2
    
            LastRow = Cells(Rows.Count, Col).End(xlUp).Row
            
            Application.ScreenUpdating = False
            
            With ActiveSheet
                For R = LastRow To StartRow + 1 Step -1
                    If .Cells(R + 1, Col) = "" Then
                        .Cells(R, Col).Copy
                        .Cells(R + 1, Col).Paste Shift:=xlDown
                    End If
                Next R
            End With
  
            Application.ScreenUpdating = True
            
End Sub