Masturbating

Only if she is wearing them.

I used my daughters to jack off on. Before you say anything she is past the age of 18.

If you're lucky enough to have a sister, and she's still living at home, then yes you can sniff her knickers, wear her knickers, wank into her knickers, she'll never know (unless you want her to catch you)

Perfectly normal. I did it in mom's panties. When she'd get drunk, i'd roofie her & shag her. It felt a little weird with the previous guy's load spilling out of her.

Depends on if it's her clean panties or dirty panties. If she's going to be putting them on after you've wanked into them than it would be more of a grey area but all in all I don't personally think either option is all that wrong but you'd run the risk of her noticing if they've been freshly used by you.

It’s absolutely ok and perfectly normal

Why not just cum inside her

The fact you ask is entirely enough for you😂

I use to do it to my mother and sisters panties

Yes, I wank in your sisters knickers regularly