Well, firstly and to get it out the way, us step-dads get it much easier. Apparently for a man to take on the task of helping raise someone else's children is a monumental sacrifice against our manly man man natures and we deserve unending praise.
Step-mothers, on the other hand, are clearly just shifty characters trying to eradicate the real mother's very existence. And probably enslave the kids or feed them poison apples or something.
Despite the fact we're doing pretty much the same things.
So yes, I get all these kudos from my girlfriend. I have a keychain she bought me. It says "Anyone can be a father. To be a stepfather takes a real man." And I get it. It's lovely. This family is my life really. It's a bit like being a dad with the added stress of constantly remembering that I'm not actually one and making sure it doesn't look like I'm trying to be one whilst making sure that the girls know they can always depend on me but their daddy is still the most important man in their life and aaaaaaaargh.
I got a text from my eight year old SD the other evening when it was a little past her bedtime. I was on the way home. It read "When are you home? Mum and dad are arguing :( " The argument was actually my girlfriend trying to tell her ex on the phone that she couldn't talk now because the kids were awake and would hear, but it was touching that she trusted me that much. I guess that's what it's about, the dependability.
As long as my girlfriend recognises that if her ex gets a new steady partner, she's allowed to be great too. (Which she does, thankfully.)
I see 'stepping up' as doing a lot of things that maybe do cross the lines a bit - helping with homework, making their food a share of the time, being seen to be involved. Sitting down and relaxing when mum has a chance to sit down and relax.
The reason I think it's important to step up is this: My girlfriend left her ex because she did everything. Like, everything, and hated the thought of her little girls growing up perceiving that as normal. If I disengage, if I step back instead, they see the same thing. I act as half the parenting team because that's what my girlfriend wants her girls to expect from their relationships.