Think about this
sexe1, I understand where you're coming from and ideally that's the way things should be. But in reality, IMHO, children do matter in love relationships.
First of all, it's critical that the one without the children had better like children and have a sense of responsibility and awareness of how to be a good parent because they will become a part of their lives.
Second, the children should like and respect you because if they don't, that spells trouble that can strain a relationship.
Third, the couple needs to have that conversation about the children and establish some ground rules. Can the non-parent chastise the children, can they be left alone with the children?
People should always be very, very careful about introducing new people in their children's lives. Particularly mothers with daughters. I just think that when children are involved, there's more to it than just the two adults who are attracted to each other. As much as we might like to think that they aren't, children play a key role in who we get involved with.
From my point of view, it's never superficial to think twice, delay or decide not to get involved with someone if the children can't cope with a new relationship for a parent. It could be the difference between harmony and chaos in the home.