Short answer. Yes, to a limited extent. An appeal by one of several accused does not affect co-accused who did not appeal, except insofar as the appellate court's judgment is favorable and applicable to them. A non-appealing accused therefore shares in a favourable outcome, but is never placed in a worse position by a co-accused's appeal.
What the law says
An appeal taken by one or more of several accused shall not affect those who did not appeal, except insofar as the judgment of the appellate court is favorable and applicable to the latter.
Rule 122, Section 11 — Effect of appeal by any of several accused. Read the full provision →
The general rule: an appeal is personal
The Rules provide that an appeal taken by one or more of several accused shall not affect those who did not appeal. An accused who accepts the judgment and serves the sentence is, as a rule, bound by it; the case moves to the appellate court only for those who elevated it. So if the appealing co-accused loses, or has the penalty modified against him, that outcome does not reach the ones who stayed behind. Their conviction became final as to them when the period to appeal lapsed without their filing one.
The exception: a favourable and applicable judgment
The rule carves out one situation — except insofar as the judgment of the appellate court is favorable and applicable to the latter. Both words carry weight. The ruling must be favourable: an acquittal, a downgraded offence, a reduced penalty. And it must be applicable: the ground on which the appellate court ruled must hold equally for the non-appealing accused. A ruling that the prosecution failed to prove the crime itself would ordinarily apply to everyone convicted of it; a ruling that rests on a defence personal to the appellant — an alibi, for instance — would not.
What perfecting the appeal changes
The same section adds that upon perfection of the appeal, the execution of the judgment or final order appealed from shall be stayed as to the appealing party. Note the limit: the stay operates only for the accused who appealed. A co-accused who did not appeal cannot ride on the appellant's stay — the judgment can be executed against him while the appeal runs, subject to his later benefiting if the outcome proves favourable and applicable. The section also keeps the civil and criminal aspects apart: an appeal by the offended party on the civil aspect does not affect the criminal aspect of the judgment.
What a non-appealing accused should do
Do not treat a co-accused's appeal as your own safety net. Whether to appeal is a decision each accused must make within the appeal period, on advice about the strength of the grounds — the exception only rescues those left behind when the appellate ruling happens to be both favourable and applicable, which nobody can promise in advance. If a co-accused's appeal has already succeeded, the practical step is to bring that judgment to the attention of the court handling your sentence, through counsel, so the benefit can actually be applied to you.