A.P.
E.,
First, congratulations on your impending arrival! Babies are such a blessing.
Our family has a yours, mine and ours and it's been pretty terrific! My son was 12 when I met my husband. My husband has a daughter, she was 6 when we met. The 2 children took to each other immediately and when we married they were happy we were all going to be a family. My husband and I had the "ours," a beautiful baby girl, two years ago. The older kids couldn't have been happier. In a way we feel like it cemented our bonds with each other. The two older children will always be linked to each other through the "ours" child.
As far as how you cope with the challenges of a blended family, much will depend on the relationship you and your boyfriend have with each other's children. The children are really too young to understand the family dynamics, especially the one-year old. I have heard that the younger the children are when bringing two families together, the easier the bonding process. Loving and respecting each other and all your children is important, but you will also need to know your respective roles in parenting the "yours" and "mine" children. You and your boyfriend will need to decide this and then be consistent in how you handle the inevitable challenges that come with raising children.
In the end, children will thrive in a loving, caring household where the parents model the kind of behavior they wish their children to emulate. Keep that in mind and you'll do great.
A.