Russell's answer hits the essentials, and I've given it the checkmark. However, I will add some more details.
Ken Matingly was engrossed in his work and had a steady girlfriend. As a New York Times article about him described:
Many say that Commander Mattingly remained a bachelor for so long to study night and day to win an assignment on the Apollo 13 mission in April, 1970.
Two months after Apollo 13, he married his girlfriend:
In June, 1970, two months after Apollo 13 returned to earth, he got married. His wife is the former Elizabeth Bailey of Hollywood, Calif., but beyond that Commander Mattingly declines to describe her. She is said to be pregnant with their first child [during his Apollo 16 flight] and for that reason did not go to the Kennedy Space Center for the launching.
Mattingly was so devoted to his wife, that he freaked out during Apollo 16 when he lost his wedding ring somewhere inside the command module cabin. (But that will be for a future question...) They are still happily together as of April 2020.
As described his obituary in the New York Times, Jack Swigert had a reputation for enjoying parties and having many girlfriends:
Mr. Swigert was tall, husky and sported a crew cut most of his life. He was a lifelong bachelor, and some of the other astronauts, all of whom were married, joked that he was somewhat of a swinger. One of his sisters once said he had ''a girl in every airport from coast to coast.''
He used to say that he was not a confirmed bachelor but that it was just that he had just not met the right woman. As an astronaut, Mr. Swigert lived in apartment near the Manned Spacecraft Center in Houston, which he had outfitted with a beer spigot in the kitchen and an elaborate stereophonic sound system. In the living room, he had a reclining chair covered in thick gray fur.
When the movie Apollo 13 came out, one of his closest girlfriends -- who accompanied Swigert to the White House -- wrote an editorial in the Los Angeles Times defending his reputation:
He was never embarrassing, aggressive or egotistical. His own apartment was filled with pictures of airplanes and spacecraft--no Vargas prints or piles of Playboy or Penthouse. He was an avid amateur photographer. His one extravagance was a fur-covered lounge chair (for one).
Swigert was elected to Congress in 1982, but died of leukemia before taking office.