You have a relative who does not respect the line. A parent who comments on your weight, an in-law with opinions about how you're raising your kid, an aunt who asks why you're still single like it's a customer service complaint. They cross into your business uninvited, and you've spent years smiling through it, and the resentment has its own zip code by now.
Here's the uncomfortable starting point. They probably do mean well, in their way, and that changes nothing. "She means well" is the phrase families use to excuse a lifetime of overstepping, as if good intentions cancel out the comment about your second helping. They don't. And waiting for the relative to notice on their own that they've been intrusive for two decades is not a plan, because it's worked for them for two decades. The dynamic isn't an accident. The whole family arranged itself around letting it slide, you included, and nobody changes a pattern that's never cost them anything.
So you say something. By text, which for family overstepping is often the better channel, because it lets you be calm and clear once, without the dinner table audience and the escalation that comes with it.
The trick is to be clear and kind and brief, and to resist the urge to explain yourself, because explanation is an opening for debate, and family members will take it. Name the one specific thing and draw the line. Then stop.
Not the version stuffed with justification that invites a rebuttal:
Mom, I know you mean well and I love you, but it really hurts when you comment on my weight, I've been working on my relationship with food and it's been hard and when you say things like that it sets me back and I just...
Try the short version that doesn't hand them a thread to pull:
Mom, I'm not going to talk about my weight with you. I know it comes from a place of caring, but it's off the table from here on. Love you.
It's warm, it's specific, and it's done. No paragraph of reasons for them to pick apart, no case to win.
Now the part that matters, and it's a mindset, not a script: the goal of a family boundary is not to make them understand, and not to win their agreement. You will probably get neither. They may push back, sulk, tell you you're being sensitive, pull out the "after all I've done for you." That reaction is the system defending itself, and it is not evidence you did anything wrong. The success of a boundary isn't them finally seeing the light. It's you holding the line regardless of whether they like it. The relief you're after doesn't come from them admitting they overstep. It comes from you no longer waiting for them to.
You can love someone and refuse the behavior at the same time. Say the line warmly and keep it short, then hold it even when they don't applaud.