I've stumbled on a couple of things that may be of interest: 1. Nightjet website offers family compartments on Nightjets, but not in Hungarian Euronights Zurich to Vienna, Budapest, Zagreb, or Berlin to Budapest. MAV does, and sometimes at very reasonable prices. 2. MAV is actively promoting its night train from Budapest to Rijeka and Koper as being formed of 1970s and 1980s stock as the "Retro Istria express train" again with very reasonable fares...you can have a single sleeper tonight for 92 euros.