  We summarize here the observed properties of ``infrared companions'' to T
Tauri stars and argue that their observational properties are identical to
those of Class I sources. They may therefore be embedded protostars in a much
earlier evolutionary phase than T Tauri stars, in which case these multiple
systems are significantly non-coeval as opposed to the majority of young binary
systems. They would have formed through a different mechanism than core
fragmentation. The only distinction between IRCs and Class I sources is that
they lie within a few tens of AU of a T Tauri star, and so they cannot be at
the center of a vast optically thick envelope as is believed to be the case for
protostars. We discuss whether systems with an IRC are really candidates for
non-coeval multiple systems.
