§1. An appeal made by the petitioner also benefits the respondent and vice versa.
§2. If there are several respondents or petitioners and the sentence is challenged by only one or against only one of them, the challenge is considered to be made by all of them and against all of them whenever the matter sought is indivisible or a joint obligation.
§3. If one party introduces an appeal against one ground of the sentence, the other party can appeal incidentally against other grounds within the peremptory period of fifteen days from the day on which the original appeal was made known to the latter, even if the deadline for an appeal has passed.
§4. Unless it is otherwise evident, an appeal is presumed to be made against all the grounds of a sentence.
Source: Code of Canon Law (Vatican.va)