Not really ancestors, more related through the adoption of an orphan.
If you want the family roots of the MG5, that is based on:
The Roewe Ei5, which is based on:
The Roewe i5, which is based on:
The Roewe 360, which is based on:
The Roewe 350, which is based on:
The Buick Excelle, which is based on:
The Hyundai Lacetti
Beyond that the trail gets muddier (if it wasn't muddy enough already) but it seems there's lots of related GM hardware and possibly a SsangYong connection.
So there.
The above was put together via a lot of trawling and should be regarded as nothing more than something from apocryphal to wildly inaccurate.