Do I have to invite my uncles new step kids???

No

Is your wedding in September 2019? If so, slam on the brakes on invitations and reassess in 18 months

If you're having a kid free wedding anyway

I wouldn't invite them. Are they under an acceptable age limit? Like, you wouldn't invite someone under 18, etc.

If you are having a child free wedding, start by defining the age you see as a child. If they are under that age, they need not be invited. His adult children get their own invitations.

I think you can stick to the no kid rule. If your cousins are adults and the step-kids are not it is ok. If any of the step-kids are over 18 they should be invited. If you are making exceptions for other kids then you might have a problem.

If it's a 2019 wedding it's far too early to be worried about.

But, if they live with them and/or he's active in their life the same as his biological kids, then I'd say it's an all or nothing, but each family is different. (Caveat You can do all kid free or kids of a certain degree, but yeah, I'd say if they live with him and his wife and you're including cousins at the same age they need to be included)

The question to focus on, is the age cut off for your kid-free wedding. The fact that he has step children should not be an issue at all...treat their family unit the same as anyone else's.

Your wedding is not for TWO YEARS. Take it form me as we rescheduled from 10/1/16 to 10/7/17......don't even THINK about guest lists until Spring 2019. Many people will come in and out of your lives.....but to help answer your question: Don't invite ANYONE out of obligation. So don't invite them. If uncle gets pissed, oh well......best wishes to you!

Don't do invites yet. Come back to it in a year/ year and half and then see if that all still holds true.

I've been to a kid free wedding. It was cool. I was considering it myself. Too many kids on my FH side. When time comes to invites, talk to your uncle. Till now enjoy your engagement