I am also a divorced mother. I have two boys, ages 3 and 6. I am dating someone too. My boyfriend is also divorced and has a 2-year-old son. He knows, as do I in reversed situations, that our children will always come first. We have talked about this MANY times and we both feel that if our children didn't come first we would be less of a person/parent. If he didn't love his son as much as he does and put him as high as he does on his list of priorities I would NOT be with him. I have dated men before that admitted to not seeing their children in at least 5 years! I could never be with someone like this.
But on the other hand we NEVER let the other person feel left out with our kids. My boys ADORE him and actually say they're not momma's boys but they're "Bailey's boys". I ask if their daddy's boys and they say "No! We're Bailey's boys". He is gone now (with the Marines) and they ask for him EVERY day. My bf is bald (he is bald on top so shaves his whole head) and now my boys want to be bald.
If my bf EVER asked me to put him first I would KNOW that he cares more about himself than either me or my children. I would only want to be with someone who puts me and OUR kids first.
If there's something that he wants and something that my kids want we all come to a mutual agreement on what we should do together as a FAMILY. (His son lives 4 hours away so he saw him about every 3-4 weeks for a week at a time before he left for the Marines and went across the country.)
I recommend you sit down with BOTH of them and see if you can come to an agreement. It's not about you, him, or your daughter...it's about ALL of you now being a FAMILY and families need to sit and work out their problems TOGETHER with everyone putting in their suggestions and coming to a mutual agreement on how things can work out for EVERYONE involved.
Good luck.
B.