"They are very cute together and have great energy, Rob seems very happy. FKA seems to be a great fit for Rob. (They) seem to enjoy the same things," a source close to the 29-year-old actor told people.com.
The "Twilight Saga" star and the 27-year-old singer, who are currently living in his Beverly Hills home, workout together with celebrity trainer Harley Pasternak "almost daily" and "enjoy walks around Venice Beach".
The insider added: "(They are) generally very active (and) both seem to enjoy staying fit."
The duo, who were spotted attending an event to benefit earthquake victims in Nepal last week, are also "involved with charities" together.