Definitely a Synodontis, not likely to be nigriventris or contracta with the ~4 inch size info here, it would need to be a much clearer photo to say much mor than that given there are sadly heaps of hybrids in the hobby. Synodontis nigrita is a possibility, but regardless, as it matures there is an increased risk of fighting with your presumeably bigger Synodontis euptera.
Two is often a bad number for same or similar species like this, one is likely to get bullied by the other, all you can do is provide plenty of hiding places for the two synos (often a reason for fights) and keep a good regular eye on them both for signs of intense battles (my 5x2x2 has Synodontis notata; decora; brichardi; flavitaeniata... by and large them all play nicely, but unusually the Pyjamas seem to be often covered in minor battle scars from each other despite being at the placid end of the syno spectrum).
