the doctors wife (we know she amy and rory's daughter) but in SiTL 2 parter river tells the doctors his name and at the end the doctor says there only one reason i would tell you my name.
I just can't see that reason being that she is a companion's daughter as he never told any of his companions his name so why would he tell one of their daughters
Unless he tells her at their last meeting before she goes to the library as he knows that she knows his name then and to make his younger self trust her

She knows his name because she read it off the side of his crib

Its 95% likely that River and The Doctor are married. I am reserving 5% because the Moff could still surprise us.

his wife (like alot people think)