Are you only looking for games in English? If so, here's some RPG/relationship games in English that haven't already been mentioned:
* If you have a Windows computer, you should be able to play the freeware RPG Maker game Love and War. Learn more about it here:
http://antioch.snow-fall.com/law/archive.shtml* Heart of Fire, Elven Relations, and Heikou are freeware games. At least 2 of the 3 were created with Ren'py, and should work on all modern computers. You'll find them elsewhere on this forum.
* Agarest War was released in English on Xbox 360 (both DVD-ROM and paid download) and Playstation3 (download only). It looks like the English version of Agarest War Zero will be released in June 2011, and will be available in both physical and paid download formats for PS3 and 360.
* The PS1 game Bloody Bride: Imadoki no Vampire is mostly a complex dating simulation, though it has some RPG gameplay. It was fan translated a few years ago.
* Eien no Aselia -Kono Daichi no Hate De- A worksafe version of this adult RPG for Windows was translated by Dakkodango a couple years ago. Jast plans to release an official translation under the name Aselia the Eternal.
* Galaxy Angel and Galaxy Angel Moonlit Lovers (both for Windows) are combinations of real time strategy and romance game. Both have fan translations.
Some RPG/romance games with adult content:
* Knights of Xentar, which is a localized version of Dragon Knight 3. It was one of the first adult games released in English.
* Brave Soul, which is basically Diablo with romance sidequests. It was released by Peach Princess on Windows a few years ago. Not too much explicit content. The game has been known to crash when the combat gets too intense... I don't know if there's a good patch or work-around.
The same company also translated Pretty Soldier Wars A.D. 2048. I haven't heard many good things about it...
Castle Fantasia 2: The Sacred War Renewal is an adult RPG with a fan translation.
Men at Work! 2 ~Hunter Academy he Youkoso~ was translated by Mirrormoon a few years ago.
Utawareru Mono was translated by a short-lived group.
Dakkodango also translated Tears to Tiara for Windows.
Fans have translated both Sengoku Rance and the vintage game Rance -Quest for Hikari-. This series is known for being explicit.