We know very little about Darth Plagueis in canon, and almost all of that information comes from his apprentice Darth Sidious. We don't know from canon whether or not Darth Plagueis even succeeded in resurrecting anyone from death. It's possible he didn't since Sidious claims to have learned everything from him yet Sidious also told the newly minted Vader that he didn't know how to cheat death.
In Legends, we do know that Darth Plagueis succeeded in resurrecting a Bith named Venamis:
On the same day they had allowed Venamis to die.
Then, by manipulating the Bith’s midi-chlorians, which should have been inert and unresponsive, Plagueis had resurrected him. The enormity of the event had stunned Sidious into silence and overwhelmed and addled 11-4D’s processors, but Plagueis had carried on without assistance, again and again allowing Venamis to die and be returned to life, until the Bith’s organs had given out and Plagueis had finally granted him everlasting death.
Darth Plagueis, p. 279
Darth Plagueis used Venamis for experimenting with his resurrection techniques, but Plagueis obviously didn't care about Venamis given that Plagueis subjected him to this kind of experimentation.
The same Legends source indicates that Darth Plagueis was able to heal himself, although he was of course unable to save himself from death.
Sidious was stretching the truth for Anakin in order to persuade Anakin to the dark side. Sidious knew Anakin wanted to save his loved ones (e.g. his mother) from death, so Sidious was tempting Anakin with the possibility of being able to do so with the help of the dark side. As a Sith, Plagueis probably didn't care about anyone but himself -- but the fact that he could save anyone (except himself) from death means that he theoretically could save someone he cared about as well.