I do agree with Ny in terms of commitment and emotion. When my husband stated dating his girlfriend, I told her that I didn't believe in any hierarchy of affection. I, in fact, have put my friendships on equal terms with my feelings and responsibilities toward loving my husband.
However, we ran into a problem. That problem is simply regarding the "work" that it takes to run a family. My husband works most nights, we have a child, and numerous pets and other household concerns. His girlfriend wants to have her relationship entirely separate from me and his family. As a consequence, I've had to work on putting my needs for help in the household above her needs (for him to spend the night once a week, when he is already gone 3 nights a week and all Sunday). But, again, this is just practical. If we didn't have a child or if she didn't want their relationship entirely segregated from us, it would definitely be a different story.