I think the issue is boundaries, not who is loved "more". I'm dating a man with children. He is a good father who is very involved with his kids' lives. He is also a good boyfriend who meets my needs. It's a matter of mutual respect and setting clear boundaries.
When we first started dating, his kids sometimes had a hard time with the fact that he was not always available. He pointed out to them that they have play dates with friends. So he asked them - is Dad allowed play dates? That helped them understand.
By setting healthy boundaries, he is showing his children that they can also set healthy boundaries.
Growing up, I always knew my parents loved me, but they also loved each other. When children see their parents take care of their own needs that helps them realize that it's OK to do so. When children see their parents fall in love and form healthy adult relationships, that gives them healthy patterns for their own lives.