Charles Ingalls was 4 years older than Caroline Ingalls, which is actually a fairly small age gap for this time period. Charles Phillip Ingalls was born on January 10, 1836 while Caroline Lake Quiner was born on December 12, 1839. Caroline had just turned 20 years old when she married Charles.
The age gap between Laura and Almanzo was much greater, with Almanzo being almost ten years older. Laura was only eighteen when they married while Almanzo was 28.