Here are the rules according to TG (actively dating, while raising two teens). These only apply to divorced people, widows/widower is a different dynamic that I haven’t put enough thought into.

1. I’d never date someone without children again, they have too much free time that I can’t match and they don’t get the next rule.

2. I’m never meeting her children in person and she’s never meeting mine unil they are old enough to vote or at least drive, but voting age is preferable.

That’s it, that’s all you need to do to raise completely healthy kids. All opposite sex adults are a threat to their time and love from their parent. Grown up, divorced parents have one priority in life, if they seek a diversion or physical contact then discretion and privacy is the only way they can accomplish it. Most divorced parents share custody equally these days so it’s easy to have two lives and keep them apart, having to confine all of your affection, adult companionship and sex into two or three days a week is completely workable and most married couples do that anyway. The best single mother’s I’ve met share this philosiphy and the mother’s that want to move in together/merge families/meet each other’s kids aren’t very good mothers anyways and end up not being the type of women I’d want my kids to meet. I’ve met a number of women over the years who seem to move in with a new guy every year or so and bring the kids along, having to move out when there is a fight or they realize they don’t like each other. That’s no way to establish the comfortable, solid place that a child calls “home.”