SiL and friend keep commenting on my age.

I'd shelve the friend as far as I could, but I guess you're stuck with your SIL.

As tempting as it must be to stick the boot in, I would rise it above it. I always think it's not what* *people say but why they say it. She clearly has a problem with the idea of ageing and for some reason she's choosing to make herself feel better by trying to make you feel worse. And it's working. Don't give her the satisfaction. I'd take the position of a confident, wise sage and adopt an armchair psychologist approach in the kindest possible tone: "You seem to be quite fixated on my age and how I look. I wonder why that is. Is ageing something you're struggling with?"

Then reinforce all you've said here about how healthy and strong you feel, and how you're embracing the years of experience and wisdom you've accrued.

She'll hate it!

"At least I don't look my age" <pointed stare>

One of my husbands younger friends much younger wife always brings up age when we are together. She’s a decade younger than me (and gorgeous and a really impressive mum). I’m not frumpy and chaotic and seriously not a threat in any way. It baffles me. It’s been 20 years and I’m still older than her. I think my indifference to that baffles her.

This! Perfect - will end it totally.

Oh love this!! As others have said, they’re projecting their insecurities. You can’t choose your in-laws. Stay integral to your own values and don’t let them drag you down to their level!

Do make sure you spend time with people in your life who life you up rather than drag you down to dilute the toxic ones if you are keeping them in your life.

My friend is 5 months younger than me and never lets me forget it. Each milestone birthday she'll ask how it feels to be that age. One day she was in the car with me and my boss asked if she was my mother! I've never told her lol.

😅😅 THIS OP!! Pleaaase Use This!!! 😭

How annoying OP my sister used to do similar when I'd turned 40 and she was still 38 knowing I was sensitive about it. It doesn't sound like you're worried about your age though so I'd say it's an insecurity on their part and the fact you're aging better!

Pretty obvious what’s going on here & it’s jealousy. You are 5 years older but fitter, look younger etc.
if she’s had cosmetic surgery & it’s not turned our great (dr spok as you put it) then she must see this every time she looks in the mirror. This however is no excuse to have digs at you for absolute no reason.
Honestly ignore her smile when she insults you & try & spend as limited time with her as possible. She needs to sort herself out & get over her insecurities.

I had years of this but the other way round. I'm younger than DH, and the youngest of his siblings. I used to get "oh you'll understand when you 'grow up' a bit" or "yes, but really you're still a baby".

Even in the early days of our relationship, I was more mature than the "youngest" couple, despite being 5 years younger than either of them".

I just ignored it, and then one day just asked one of his brother's if he was jealous DH has a young wife, seeing as they mention it so often. It stopped then.

People who are fixated on someone's age are usually fixated on the fact that they are aging and no longer have their youth or looks. Or jealous of something else about you. I'd just roll my eyes if I were you. And one day the perfect response will present itself. Say it.

This. 'Yes, I know, and everyone thinks you're older than me.' With a big, calm smile. On repeat. She'll soon stop bringing it up.

Just say, yeah, good job I dont look it!

Sorry... 'smile sweetly'

My reply?
"What an odd thing to say out loud. Sounds like you're feeling emotional. Hope you're ok"
Emily sweetly

I'd just say.. randomly.. God, celebs have been aging poorly in the last few years with all the procedures to their face, it's sad they feel so insecure about themselves, same with the people too lazy to run for a bus, get fat pumped into their bottom to try and fit in with the kids 😂

"I know right? I'm so lucky I look so great for my age"😜

Treat the absurd with the absurd. You’re not insulting them or their looks, but you are treating their statements as ridiculous. It takes the heat from their statements and means their arrows don’t hit their mark. Sometimes people just say things for a reaction - to make themselves feel good. Responses like these take the wind out of their sails.

Oh, God you’re so old
Not sure I want to hang out with elderly people

Sure you do, Janice. It’s only 5 years. You’re in the zone now. Welcome to Menopause Land.

Then there is my SiL who constantly refers to the fact I am 5 years older than her. Things like;
**
You are much older than me

And I still have all my own hair and teeth (waggle eyebrows, flashy grin).

I’m much younger than you

You’re little more than a tiny child, Sandra. That is true.

Well, that’s because you are a lot older than me, I’m only 48, and you are 53

I know. Your balls haven’t even dropped yet.

Perfect! (laugh after you say it)

Short and succinct.

They are Jealous. As. Fuck. The green eyed monster is eating away at them and they have to keep grasping at the one tiny thing that makes them feel better.

I LOVE the biodegradable comment.

What else ...

'Here's a tip - if you can't say anything nice, don't say anything at all. It makes you look ... better. If you know what I mean.' (Smiling sweetly).

'And I'd be delighted to give you some ideas on diet and exercise and makeup and clothes and so on. I know it preys on your mind that you're looking older than me. I imagine it must be difficult?'

I find the problem with rising above this behaviour is that it gives the person carte blanche to continually repeat it, knowing they won't be called out.
Personally, I'd stop it dead in it's tracks with a random offensive retort, and then claim I thought we were playing a parlour game.

SIL: "Well, of course everyone knows you're so much older than me".
OP: "Well, of course, everyone knows it's you continually farting. You sound like a warthog beat-boxing with a kazoo.

[Cue awkwardness]

Sorry, am I not playing this game correctly? Oh well, never mind. Nice weather we're having..."

It's harder to argue with 'crazy'.

I like the idea of getting her an enormous 50th bday card and balloons, etc, and giving them to her when she’s 49

And this!

This!

This is bizarre. Your SiL and the other friend sound extremely immature.
I have some very close friends 12-15 years older than me and the only time I would bring our age differences up is in the context of "what can I expect" when discussing our kids, as their kids are teens and 20s while my DS is still a little kid.

I suggest a response along the lines of that my DD15 delivered to her best friend yesterday ("I haven't got the energy for your dramas at the moment, so I'm taking a break from you") or deliver your quote (to which my DS12 would cackle with delight and declare it "roast of the century").