Hi Wild,
In the end only you can decide if this is the road for you.
For me, I was never really into kids when I was a kid. I have a sister who is 9 yrs younger than me and she was not an easy child for my parents to raise. I was old enough to see how bad it was before it can get really bad. My sister was a pain but never got in trouble with the law. She now has kids of her own, a good paying job and a loving husband.
For awhile, I was a fencesitter but leaning towards no kids. It was external pressure making me doubt my choice but eventually hubby and I decided no kids was the best choice.
Regrets? None so far and I have reached an age that having my own naturally is no longer possible. I try to spend time with my sister's children. Hanging out with them actually confirms I made the correct choice. So much work and the payback doesn't seem big enough to me to make up for it.
In your situation, you will be taking on some responsibility with your partners children. Not an easy situation even in the best circumstances.
I suggest talking it through with your partner and possibly getting some counselling to talk it out with an impartial party. You still have lots of time to consider the situation. Some deep soul searching is required.