I guess to some extent it could vary depending on the situation. I know a couple of people who really do blend all their ex's and various skids into big old family groups for parties and whatnot.

For me, my blended family is DH, me, his kids, my kids, the cat, and the dog.

What do you consider the "blended family"?

Certainly not BM, nor her revolving door of husbands.

In my very first college sociology class, we had to give a presentation about a subject that was sociological in nature. Mine was the blended family. I took a cheap blender into class. Had photographs of DH, myself, SD, both bios, our family pets, and pieces of cardstock that had BM, her DH and his daughter's name on them.

Stuck ALL of them in the blender with a Monster energy drink, and let that sucker rip.

I got an A+.

Blended family to me is basically the people who work together to build the family up. Unfortunately for us, it was DH and Me building, the boys being the cornstarch to hold it together, and SD, BM and her DH to break it up. kinda like putting pineapple in the jello.

Used to be myself and husband, our biological daughters and that was it. His sister and her husband were often there. My SD would always whine even as an adult to go to her BGP House for holidays/her BM died close to 30 years ago. Now that those BGP are dead, for the last two years that was out of the mix. At that point we added in my BD and husband and my BGK. My SD was not happy with the BGK in there. Now that my husband has died, my blended family is my daughter her husband myself his parents my BGK and his BC. I would like to add in my husband's sister and her husband but it gets way too confusing. My SD and her significant other don't want anything to do with even her Her father sister or her uncle. She's too interested in the family of SO.

I don't think there is ever A blended family that stays blended. Right now in my time and my space it is my BD And her husband and my BGK  and my SGK. Who knows how long that will last because both of them are older teens.

Who knows how long that will last because both of them are older teens.All I want for Christmas ( or any other holiday for that matter or any family gathering) is the group invited with no drama. Hopefully that will occur. Last year my SIL had his ex claim "she had Covid" so his kids could not come. Turns out she never had it she just wanted the kids all Christmas. This year, she has the kids on Christmas weekend and is refusing to allow them to go see their father. I have no idea what she has a hold over them. It's creepy. The kids come true by BDs  house at least three days a week and everything is fine.... this woman is obviously having issues over the fact that my SIL married my BD. That means that now her kids have a SM who is my BD. ....

It's never easy you just have to go with the flow. I'm just glad my SD has taken her self out of the flow

all SKids in their relationship regardless of kid parental biology, and any joint children for that couple are the insular blended family.

Also part of the mix but not in the insular element of the actual family are the families of any Xs that either partner has bred with in a prior relationship.  Though for me, and in a significant % of cases, those folks are the blended family opposition.

The blended family is likely a far larger entity for the kids than it may be for their parents.  The kid could have to blend on either end of their gene pool.  Parents may not have to do that depending on if they marry a prior breeder or not.

For us, SS-30 is an only child in our marriage. He has 3 younger also out of wedlock Spermidiot spawned half sibs by two other baby mamas on the SpermClan side of his blend.  However, his closest  relatives relationship wise, beyond his mom and I iare my family.  He has a relationship with my IL clan though not particularly close.  He is extremely close to my parents, my brother and SIL, and their kids.  SS asked me to adopt him when he was 22. Making what I have always been a documented fact. I'm his dad. 

The defition is highly fluid and variable for each situation and even potentially variable for some individuals in the blended family.

IMHO of course.

significance.  The group she considers the blended family is not the blended family for her. It is only the blended family for the SKid.

The Xs who want to remain relevant to their own X pull this kind of thing out of their own ass.  Which is about what it is worth IMHO.

Blended family is a dumb, made-up, meaningless term IMHO. Who wants to be blended? That sounds awful. 
I call it a mixed family or step-family. Me & DH and my bios are the primary mix. DH and his BioDiablas are a different mix. SD's made it clear they have no intention of getting to know us, so as far as I am concerned, they are not a part of any mix that includes me and my BK's. 
BM is SDiablas primary parent (in their own minds) because she painted herself as the victim, even tho she was the violent aggressor that rode DH's gravy train since they met and even tho DH provided the lifestyle that SD's (& BM for that matter) enjoy. BM saw their, now failed, marriage as transactional. DH gave and she took, took, took and screamed "I want more!"

I guess her husband would then be YOUR blended husband, right?  Hahah

Are YOUR children her children?  Of course not. She has zero relationship to YOUR children. Where does she get the nerve to lay some sort of familial claim to them. 

Ridiculous. She is trying to make it seem like you are all one big happy co-mingled bunch when you are not. 

Nooooo. I hate the word blended. This is not the Brady Bunch. SD12 is technically a half-sister to DS(almost 2). She doesn't act like a sister, so I don't consider him to have any siblings. Face-to-face, SD ignores him... and on social media I've seen her mocking him and calling him names. Sure, DH may have "another child from a previous marriage" as I like to call the situation... but there is no brotherly love about it. DEFINITELY not any blending going on. 

The blend is the three of us.

It is simple when there is only one spawn in your home.

Me, my kids, DH, and sd (even though she is more and more not part of our family).... we might not be thoroughly blended, but we're blended enough lol

Me, my kids, DH, and sd (even though she is more and more not part of our family).... we might not be thoroughly blended, but we're blended enough lol

My blended family is me, DH, DD and the two SDs.

The SDs are also part of a blended family that includes BM, her husband, the husband's son and the SDs. 

My husband, DD and I do not blend with BM's family. 

I dont believe in blended families, there are no such things. My family for me is basically anyone who is blood related to me or whom I grew up with. I consider my husband as part of my family and that is the only reason I have let him slide on many things....Only because of my upbringing, i have forgiven and given many chances just like i would for a family member

His kids and exes arent part of my family....