Yes. My partner does have a child with someone else. At first it was hard. No it was more than hard! His ex and him and a lot of problems, well she did with me. When we got together I done my best at being good to his daughter without pushing myself on her or just ignoring her. She was just a toddler and she wanted my attention. I was weird because I didn't want the mother to think I was trying to take her place at all. I'm totally against trying to take over the mommy role when it isn't your place. So I distanced myself some and the mother she just never did care for me. We never had problems with each other, but she just didn't like him being with another woman. After we'd been together for a year I accepted his daughter just like I accept my own. I treated her well and my family treated her just like our own. Then on Christmas eve she had it with us at my family's house and when her mother came to get her she pitched a fit and said she wanted to give me a hug. One hug turned into "please one more!" and eventually she said "I love you" to me. I didn't want to not say it back to a child who doesn't understand, but I didn't want to upset her mother and boy she was upset! Anyways she called later when we'd left for the smoky mountains to stay in a cabin and told us the child would never see us again because she said she loved me.
Long story, but I don't mind children. I'm unable to havee them. My partner and I had 2 and lost them both and now we have my sister's kids and they are like our own to us, but we would like to see his more too.
In most situations I'd never be with someone who had children, but my partner and I've been together for 5 years and it's no issue anymore. Now I wouldn't ever do it again. It's exhausting emotionally and physically and requires a bit more thinking than with your own kids. It's hard to love a child like your own when they aren't your own.