While I'm not sure if it would be considered a miraculous thing but it wouldn't be considered a bad thing. According to Lacedaemonian mythology, the twin kingship of Sparta was founded by a pair of twins, the heroes Eurysthenes and Procles, through whom the Eurypontid dynasty (the dynasty of Sparta's golden age, during the Greek classical period) claimed ancestry to Herakles.

Furthermore, Greek mythology has many twins in its pantheon: Artemis and Apollo, Castor and Pollux, Hypnos and Thanatos, just to name a few. Obviously, if the Lacedaemonians thought that twins were bad, they wouldn't have twins in their religious pantheon and stories, and their kings certainly wouldn't claim descent from twins. As they did do these things, we can see that being a twin was perfectly acceptable culturally, and was not seen as any kind of affliction.