That's a myth. I had way more money before I got married and had a kid.
That's probably because just like most young married couples today, you went out and bought a $250-300K home , you drive a brand new 4X4 pickup, the wife drives a brand new SUV, go to Cardinal/Rams/Chiefs/Blues games once or twice a week, that a couple nice vacations a year, 4 wheelers, jet skis, hunting/fishing trips, and living the good life when you are basically just out of college and starting out in life.
God forbid young people start out in life like our parents - a modest 30-40 year old home, dad driving a 10 year old vehicle he bought with 100,000 miles, maybe ONE ballgame a year, and vacation was a day at the lake or creek.
My guess is you spend, spend, spend, to keep up with the yuppy frat boys. Don't try to tell me that you and your wife don't have more money than the average single person.