For loop with unix find

That's one of the reasons why you never use a for loop to iterate over a command whose output can contain spaces. Especially if that output is a list of file names that can contain anything except / and \0. You have fallen into bash pitfall number 1. Always use while instead. To make sure it works with all file names, including those with spaces, newlines, tabs, backslashes or any other strange characters, use this:

find /home/family/Music -name '*.m4a' -print0 | while IFS= read -r -d '' file; do
     ffmpeg -i "$file" -acodec libvorbis -aq 6 -vn -ac 2 "${file%.m4a}.ogg";
done

Explanation

• Note that I quoted *.mp4a which ensures that bash will not expand it before passing it to find. This is important for the cases where you have files that match that glob in your current directory.

• The -print0, as you probably know, causes find to separate its results with \0 instead of newlines.

• IFS= : This sets the input field character to nothing, ensuring that no word splitting will take place.

• while read -r -d '' file: This will iterate over the results, saving each as $file, just like for file in $(command). The options are (from help read):

   -r     do not allow backslashes to escape any characters
   -d delim   continue until the first character of DELIM is read, rather
      than newline
  

  Setting the delimiter to the empty string (-d '') makes read play nice with find's -print0.

• "${file%.mp3}.ogg"; : This is simply to remove the .m4a suffix and replace it with .ogg so you get foo.ogg instead of foo.m4a.ogg.

The rest is the same as you had attempted so I'm guessing you understand it.

Use xargs with -0 option, or use find's own exec option:

find /home/family/Music -name '*.m4a' -exec ffmpeg -i "{}" -acodec libvorbis -aq 6 -vn -ac 2 "{}.ogg" \;
# or:
find /home/family/Music -name '*.m4a' -print0 | xargs -0 -i ffmpeg -i {} -acodec libvorbis -aq 6 -vn -ac 2 {}.ogg

Note that in both cases (and in your original command), x.m4a will be converted to x.m4a.ogg.

This may be solution of what you want

#!/bin/bash    
find  /home/family/Music -type f -name '*.m4a' -print0 | while IFS= read -r -d '' i; 
  do
   #do ffmpeg -i "$i" -acodec libvorbis -aq 6 -vn -ac 2 "$i.ogg"; 
   echo $i
done