There’s lots of wiggle room here. Some couples are okay with age gaps, others are not. My mother was six years older than my father. In the 1940’s, it was considered too much, especially when the woman was older. Mom had more or decided maybe marriage wasn’t for her. She was thinking of making the Navy her career as she wasn’t suitable for a nun and hadn’t met anyone she wanted to marry. Until she got transferred to Lakehurst Naval Airbase and met Dad. They courted quite some time because had signed on to serve after the war. Lots of children were not in the offing due to a health issue, but they tried and two of us lived. We took in my cousins, seven of them, for 10 years, so the house was full, anyhow!
My parents were faithfully married 66 years. They lived until ages 98 and 96.