split file with awk

Shell Programming and Scripting
1

I did a lot of search on this forum on spiting file; found a lot, but my requirement is a bit different, please guide.

Master file:

x:start:5
line1:23
line2:12
2:90
x:end:5
x:start:2
45:56
22:90
x:end:2
x:start:3
line1:23
line2:12
x:end:3
x:start:2
line5:23
line8:12
2:90
x:end:2
x:start:5
someline
x:end:5

I want to split the above file with 2 instances in one file, so that

file1:

x:start:5
line1:23
line2:12
2:90
x:end:5
x:start:2
45:56
22:90
x:end:2

file2:

x:start:3
line1:23
line2:12
x:end:3
x:start:2
line5:23
line8:12
2:90
x:end:2

file3:

x:start:5
someline
x:end:5
2 
awk 'BEGIN { filename = "file" ++n }
 { print > filename }
/^x:end/ {++end}
/^x:end/ && end % 2 == 0 { filename = "file" ++n }' "$FILE"