The Incredibles were not the first pair of married superheroes to fight crime together. Who was the first married superhero couple to fight crime as a team?
I'm going to say Hawkman and Hawkgirl. Sheira and Carter Hall were girlfriend/boyfriend during the 40s, and when Silver Age Hawkgirl was re-introduced in 1961, she was married to Hawkman.
Hawkgirl was one of the first costumed female superheroes, as it is, so it will be difficult to find any married superheroes to predate them.
The earliest superhero married couple from the Golden Age were The Flash & Joan Garrick, but no known issue has shown it. Wikipedia reports it had to be between 1940 and 1951's House of Un-American Activities Committee, where The Flash was told to tell his true identity and was shown to be recently married.
Likewise, Hawkman & Hawkgirl were married in a Thangarian Ceremony sometime between 1961 and 1964, when they joined the Justice League of America.
Besides these that are unknown, there have been many Superheroes who tied the knot:
- The Elongated Man & Sue Dibney in Flash # 112 (Apr-May 1960)
- Ray Palmer, The Atom & Jean Loring (Engaged in Showcase # 34, Married ?)
- The Fantastic Four's Reed & Sue Richards in Fantastic Four Annual # 3 (1965)
- The Flash, Barry Allen & Iris West in Flash # 165 (1966)
- Yellowjacket & The Wasp in Avengers # 60 (1969)
- The Vision & The Scarlet Witch in Giant-Size Avengers # 4 (1975)
- Mister Miracle and Big Barda in Mister Miracle # 15 (1977)
- Lightning Lad & Saturn Girl in All-New Collector's Edition C-55 (1978)
- Black Bolt & Medusa in Fantastic Four Annual # 12 (1978)
- The Karate Kid & Princess Projecta in LOSH (1983)
- Hawkeye & Mockingbird in Hawkeye # 4 (1983)
- Ka-Zar & Shanna in Kazar the Savage # 29 (1984)
- Bruce Banner & Betty Talbot in Incredible Hulk # 319 (1986)
- Peter Parker & Mary Jane Watson in Amazing Spider-Man Annual # 21 (1987)
- Johnny Storm & Alicia Masters in Fantastic Four # 300 (1987)
- Scott Summers and Jean Gray in X-Men # 30 (1994)
- Clark Kent & Lois Lane in Superman Wedding Album (1996)
- Rick Jones & Marlo in The Incredible Hulk # 418 (1997)
- The Black Panther & Storm in Black Panther # 18 (2005)
and the very 1st gay marriage in comics:
- Midnighter & Apollo in Transfer of Power Graphic Novel (2002)
followed ten years later by
- Northstar and Kyle Jinadu in Astonishing X-Men # 51 (2012)
The 1st "official" marriage I could find in comic books was Joe Palooka & Anne Howe in 1949.