It is not a requirement that you file a cross petition. However, if your spouse has stated or requested something in the original petition with which you disagree, or if you have additional issues that you want the court to address/resolve, then filing a cross petition might make sense. If you have found "regular" petitions online, you can use those, just change the title and be sure to include all of the appropriate information (e.g. cause number, etc) in the caption. Also be sure to state as the first point the date on which your spouse filed the original petition for dissolution.
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