It is challenging to reliably identify stars that were born together outside of actively star-forming regions and bound stellar systems .
However , co-natal stars should be present throughout the Galaxy , and their demographics can shed light on the clustered nature of star formation and the dynamical state of the disk .
In previous work we presented a set of simulations of the Galactic disk that followed the clustered formation and dynamical evolution of 4 billion individual stars over the last 5 Gyr .
The simulations predict that a high fraction of co-moving stars with physical and 3D velocity separation of \Delta r < 20 pc and \Delta v < 1.5 km s ^ { -1 } are co-natal .
In this Letter , we use Gaia DR2 and LAMOST DR4 data to identify and study co-moving pairs .
We find that the distribution of relative velocities and separations of pairs in the data is in good agreement with the predictions from the simulation .
We identify 111 co-moving pairs in the Solar neighborhood with reliable astrometric and spectroscopic measurements .
These pairs show a strong preference for having similar metallicities when compared to random field pairs .
We therefore conclude that these pairs were very likely born together .
The simulations predict that co-natal pairs originate preferentially from high-mass and relatively young ( < 1 Gyr ) star clusters . Gaia will eventually deliver well-determined metallicities for the brightest stars , enabling the identification of thousands of co-natal pairs due to disrupting star clusters in the solar neighborhood .