The chemical fingerprint of those sibling systems should be similar to our solar system and if evolution started from scratch here, it may have started from scratch in those systems as well. If things must be just so for life to get started, sibling systems will be a juicy target for any ET search, if we can identify them.
Interesting fact: Alpha Centauri A and B are about the same size and age as the Sun. Could they be siblings? Maybe. I think the composition is similar. I don't know how well their motion tracks ours.
Alpha Centauri A and B could be from the same stellar nursery. If Proxima was bound to the Alpha Centauri system during its formation, the stars would be likely to share the same elemental composition. We can say its a “captured” heavenly body.