Howard Stark is in the first Captain America movie, and Peggy Carter Agent of SHIELD. Cap's vibranium shield was a gift from Howard Stark. They are connected. Robert Downy JR was born in 1965, so Tony Stark might have been too.
Howard was 30 something in the 50s, and not married.
As long as Howard married some one significantly younger than he was, I don't see any issue with the timeline.
Tony Stark's official MCU date of birth is 29 May 1970, which would have made him 21 years old at the time of his parents' deaths in December 1991 (which is consistent with Tony's appearance in his memory of the last time he saw them, as depicted in
Civil War). He also appeared to be roughly 4 years old in the video Howard Stark recorded for the 1974 Stark Expo.
Iron Man took place in April 2008 (based on a newspaper glimpsed in the movie), making Tony 37, going on 38, in that film.
It's somewhat awkward, though, because according to the presentation for the award Tony won at the beginning of
Iron Man, his parents died some time after his 17th birthday but before his 21st birthday (still in December 1991 though, based on newspaper clippings in the video), then Obadiah Stane ran the company briefly until Tony took over when he turned 21. But small inconsistencies like that can be chalked up to IM1 being the first movie, before Marvel had really nailed down their plans, since they weren't even sure yet if their shared universe idea was even going to work.
As for Howard Stark, in the MCU he was born on 15 August 1917, making him almost 53 years old when Tony was born. Not entirely implausible for a billionaire playboy like Howard Stark.