Will my bio kids go without?

Oy. Does your FH know you feel this way? I'd tell him so that he knows how you feel about his children...

I think you are overthinking things. Even if you start trying for kids in January 2020, that's basically a year out from now for when you'd even have your first child and that's only if everything goes 100% perfectly and that's not the case for a lot of couples. Neither you or your fiance know what your future holds for your jobs, your income, your savings, where you'll want to live, your fertility journey, your desire for future kids, etc. Some people have 1 kid and don't want anymore, even if prior they thought they did. Plus, I'm assuming your fiance is hoping you view his kids as your kids and love them all the same? In less than 10 years, his 9 year old will probably be in college or want to live on her own. Young kids like sharing rooms (in my experience) especially when they are close in age. It's when they turn 10 or so that they want/need their own space. If you are super concerned about it, I would focus on your income & savings and try to increase both so you can buy a bigger home or look in a more affordable area. If you buy a house with an unfinished basement, you can easily add bedrooms in the future.

Besides the fact that you're way overthinking it, sharing rooms isn't a big deal and it absolutely isn't something that would sully an otherwise good childhood. Not sure why you are equating those things. And considering there's no guarantee you'll even have three bio kids, it's a bit silly to worry about the needs of hypothetical children over the needs of the real, existing ones. Cross these bridges when you come to them.

Maybe off topic, but I recommend premarital counseling for everyone, but certainly for people where there will be stepchildren. I would be asking, is DH planning to pay for their college? Does he have money saved? Will his ex wife contribute.

I absolutely feel that I've had "a great life" and especially a great childhood. It included sharing a room with my sisters who were 6 & 8 years older than I was until the younger of the two got married when I was 17. I left for college a year later and had at least one roommate until I was in grad school. I met H a couple years later, and he's been my "roommate" for the last 34. So, I've only had "my own room" for about 2-3 years of my entire life! Many of my fondest childhood memories are of the late night conversations I had with my sisters. They are my two closest friends (besides H and daughter) to this day. I'd never see siblings sharing a room as a detriment, unless you're talking about concerns like opposite sex teenagers or a screaming infant and a school-aged child who needs to get their sleep, etc.

I agree with others that it sounds like you have some concerns about seeing your husband's children as your children. I think that's concerning and encourage you to seek premarital counseling. Step-parenting issues are a significant issue in the success of second marriages. Good luck to you!

I think you're looking too deep in to it. My FH has a daughter from his first marriage (now 13). We have a 2 bedroom apartment because that's what we can afford right now. Our daughter together is 3. They have ALWAYS shared a room. The age difference makes it difficult sometimes but they have a roof over their head, food on the table and clothes to wear. They don't have it all that bad. Regardless of that - you have an extra room for you first baby; by the time you were to have another baby on top of that the two younger ones can share because they'll likely share a lot of the same toys. Once your two young ones are old enough to NEED their own room you guys could either have a new house or one of the older ones could be moved out.

To be honest, you're getting way too wrapped up into something that hasn't happened yet. That's great if you end up having 3 kids, but there's no guarantee. Stressing about the number of bedrooms your future house has right now is just asking for so much added stress, and pressure.