A deep interpersonal relationship, one that finally shifts the focus from one’s self-centeredness and hedonistic desires to caring about someone else, to prioritising the other. As sad as it is to say (because not everyone gets to it), I don’t think you can be a proper mature adult without it, you’ll just be a selfish, shallow child with no patience for the other. So, taking care of a gf/wife and taking care of your children obviously belong to this category, as well as being a devoted caregiver in general.