love-
I will just say this:
Your STBSS is a very lucky boy to have such a thoughtful STBSM. It is very clear in your posts that you are serious about your role in his life, and that you make every attempt to not "overstep". It is also clear that you try to take the moral high road, even though it's not appreciated or reciprocted by his mom.

Just keep doing the right thing...it WILL pay off in the end. You will have a rock-solid relationship with him if you do. I've done the same things as you...questioned my every move with them... Am I being fair? Am I giving equal time/attention? Am I overstepping? It really has paid off with my skids. We are very, very close...and they are 15(SD) & 18(SS). DH and I met when they were 4 & 7.

Can you post "fairness is not everyone getting the same but everyone getting what he/she needs" on the fridge or somewhere else that everyone will see it often?

One idea I have for you is to have special one-on-one time with each kid. Say, one weekend day a month, you and DD go out for lunch and for the afternoon, just the two of you, and FDH takes his DS for a similar outing. Then, two weekends later, you swap kids and do it again.
Each kid would get alone time with each parent, and it would provide some extra bonding time and a little special focus for each of them...

I treat all children fairly, I try to treat everyone fairly. I can't see being a spiteful person, it just makes your life more difficult and it's childish. Even when my adult step children drove me up the wall and caused a problem with my relationship with my husband. I still treated them with courtesy. Any other treatment, just makes things worse.

I dont think OP would act spiteful. I think the problem is, even subconsioulsy, a mom is always going to regard her child as her child. As OP said in an earlier post, she didnt think it should be her responsibility to pick up stepchild every day after school. I dont disagree with that, but then OP has to recognize that she does treat the children differently and deal with it.

"As OP said in an earlier post, she didnt think it should be her responsibility to pick up stepchild every day after school."

I did say that, but not in those exact words. I truly would do it EVERY DAY, no problem, IF I did not have my daughter. But I do and I do have to consider her well-being, as well. STBSS is going to have to make the 45 minute drive from school to our house, regardless of whether it is me picking him up, fiance or a babysitter--that is unavoidable. What is avoidable is having my DD do the drive every single day.I do not think is okay for her to have to spend close to two hours in the car after school.

Maybe that is me *favoring* her over my STBSS...I guess, in a way it is...but that is the reality of the situation.

I also am committing to doing 1 or 2 days a week. 1 if we have a 3 day schedule, 2 if we have a 5...and then my fiance will do the rest.

I think that is a fair compromise.

I am not saying it isnt fair, just ask that you recognize you are treating one child as your child, and the other as your step. Some people do have children attending schools an hour apart, and they manage. I understand your frustation with the situation.

Yeah, maybe. I don't know.

I did say in another post that if they were both my bio-kids, they would not be in schools an hour apart--I just wouldn't set up a situation like that.

BUT--I hear what you are saying. My daughter is my daughter and at the end of the day...shoot me if you want....my love for her is unconditional. She is my child. I care about and respect STBSS, but, at this point, it's not the same relationship I have with DD. Maybe it will be someday, maybe not.

Tough, tough situation. Stepfamilies are hard.

I think, overall, Ceph's statement about "fairness is not everyone getting the same but everyone getting what he/she needs" is a pretty good rule to follow. Because everyone is different and everyone is going to have somewhat different needs. In the situation OP is in, the following reasons are really going to help in making it more likely to be a fair situation:

-the kids are all very young
-the kids being very close in age I think HELPS b/c they are likely to have more in common in terms of many similar needs at the same time, which will be easier to address fairly
-OP is having an active hand in raising them (which is also going to be easier b/c of the above two reasons)

The one factor that will make it more difficult to practice fairness fully is the fact that the SS does not live in OP's household full-time. And that's no small matter because ---among other factors--- it establishes a very clear difference between that child and the others. (And it also creates many sub-differences.) That is really where the SS WILL have different, additional needs from his step-siblings and those will have to be addressed and to some extent compensated for. Because the situation is already inherently unequal, the 'balance' needs to eb re-calibrated. Where this tends to become contentious is when this fundamental difference tends to get forgotten and many SP's and/or custodial step-siblings see the non-custodial child as getting "special attention" when his/her particular needs are being met. And sometimes, it's true, the compensation efforts go too far. It's a tough balance to maintain, obviously...

In general, I think, the more basic fundamental differences there are between the kids (and their circumstances), the more potential risk for unfair treatment. When everyone is on the same page (or as close to that as you can get) "equality" obviously comes more naturally b/c you just apply the same thing you're doing to all the kids. Some of the differences that can exist (which need to be taken into account) may include:

-full-time custodial vs. part-time custodial vs. non-custodial kids
-major age differences
-a kid with a physical or mental disability
-wide differences in socioeconomic level between the divorced parents

and more things I'm surely forgetting at this moment...

But there's one factor that has nothing to do with the kids themselves that I think is incredibly important in how fair, truly, things will turn out:

IF YOUR HEART IS IN THE RIGHT PLACE and if YOU TRULY DO CARE about all the kids and internally VALUE FAIRNESS as a high priority. This is a factor that can make all the difference in the world, regardless of other circumstances.

Also want to add that I think the main way that the 'balance getting re-calibrated' needs to happen is in the realm of one-on-one time the noncustodial kid gets with his/her bio-parent when s/he comes over. I don't think it's a good "compensation effort" to give the noncustodial child extra in terms of MATERIAL OBJECTS (unless, of course, there is a very specific extenuating circumstance like the kid's one passion in life is a sport that requires a somewhat expensive piece of equipment...in which case each other child should also have the equipment they need for *their* passions). I also don't think the noncustodial kid should have more lenient rules or consequences for their actions than the other kids. Really, the 'compensation efforts' should be centered on making sure the noncustodial child gets enough quality (and private, if necessary) time with their bio-parent and is not treated with HARSHER standards than a full-fledged sibling/family member than the others. The main issue is for the noncustodial kid to not feel LESS IMPORTANT than his/her step-siblings.