Both parents and in laws, within the last week.
One has offered me a car seat that they've got from someone where the polystyrene has snapped but they can superglue it back together and put the cover back on. I've politely declined and pointed out that it's unsafe and should be disposed of. They said OK, but in a way which makes it clear they think I'm ungrateful and overreacting. This isn't the first time this kind of conversation has happened - they kept offering me a newborn seat that was 10 years old, used as a toy for dolls, and been stored in a damp shed for the last few years. I made my feeling clear then.
The other...they have a car seat in their car for my youngest and have turned it around to be forward facing. They are old enough to be forward facing, legally. But it's safer for them to still be rear facing, and I've explained this and said I want them rear facing as long as possible. They haven't even told me they switched it, my eldest child grassed them up, and it was only this morning so I haven't raised it yet.
I know car seat safety has changed a lot over the years. But am I being unreasonable to expect them to understand, or at least respect what I'm saying to them - as the parent.