Well, Monster Rancher is similar, but I don't think I'd call it a "clone" per se.
I've heard that Cute Knight Kingdom is pretty similar, though.
"Proto-Indo-European makes the damnedest words related. It's great. It's the Kevin Bacon of etymology." ~MadrugadaSeveral games of Hanako, including the already mentioned Cute Knight series. Look under life simulation.
The flash games [My Pet Protector](http://www.kongregate.com/games/undefined/my-pet-protector), [My Pet Protector 2](http://www.kongregate.com/games/undefined/my-pet-protector-2), and [Project Princess](http://www.kongregate.com/games/HJECobra/project-princess) are all reminiscent of Princess Maker.
Of the three, My Pet Protector 2 is by far the best, with a fascinating character creation process. It does, however, focus more on dungeon crawling than PM does. Project Princess is an obvious, low-quality clone of PM 2 which could substitute for playing the actual game.
The indie game Spirited Heart is similar to Princess Maker 2, with some interesting twists. In Spirited Heart, the female main character starts off life on her own at age 18, and essentially raises herself. There are several male NP Cs as romantic options.
Demo is free, full PC/Mac/Linux game is $20. Gamertell's review ( http://www.gamertell.com/gaming/comment/gamertell-review-spirited-heart-for-pc ) was relatively positive, while Girl Game Review didn't enjoy the simulation gameplay ( http://girlgamereview.blogspot.com/2010/10/spirited-heart.html ).
I have recently been playing Spirited Heart. Yes, it is similar to the more familiar Princess Maker 2 in that both involves resource management with intermediate and final goals defined by the player. Another similarity is the need to save games frequently to hedge against bad dice rolls and random encounters. Unlike Princess Maker 2, cash management is somewhat easier in the normal mode, while noticeably easier in the easy mode.
Of course .... there is another similar game: Slave Maker! I found it rather funny once I realized that my job is to train well-known anime/video-game heroines into sex slaves.
As for life-sims, I think it definitely occupies a niche, although it is still relatively small compared to more popular game types. In my own case, I tend to like life-sim games like the above 3, because I tend to stop-and-go as a player and like to make up things and try differnent things out as I play through.
Since my last post, an expansion has been made, called Spirited Heart: Girls Love. If you buy it, then five girl romance options will be available.
It was only recently that I replayed Spirited Heart, and remembered that it's challenging. Save scumming can help, but there's a lot of setbacks that can occur at any time. (I had similar experiences with the fan translated version of Tokimeki Memorial Girls Side, where I'd save after every few days of gameplay, and use at least three save slots.)
There is a Chinese game called Prince Maker Braveness. Similar concept and gameplay, but the player raises a young man. One group has made efforts to translate it, but they've been silent for a few months... See http://princemakerproject.wordpress.com , and try to contact and encourage them.
I know of two Japanese games which are thematically similar to the Princess Maker franchise, but which are also about raising guys. "Dear My Sun!!" and "Angel Profile" are both Playstation 2 games from 2007. I don't think anyone's discussing potential translations.
Marchioness' Teacup is a freeware game in development on the Lemma Soft forums. If you read the creator's initial statements on page one at http://lemmasoft.renai.us/forums/viewtopic.php?f=16&t=10732 , then you will notice the person is striving to make a game similar to the Princess Maker series.
Just out of curiosity, since that type of life management sim seems to have its own devoted fanbase.
Real life has become a mountain that must be conquered epically. Cutting back on intarwebz for a bit.