Forced sharing?

How would you guys handle this?

I have twins who just turned 3 two months ago.

When they are playing with a toy, if one wants the toy, I tell the other one that they have to wait their turn, and tell them all the other toys they have to play with.

It is almost ALWAYS my daughter who has the toy then my son wants the toy.

My sister in law and mother in law are very critical with how I handle the sharing, and believe my daughter should have to give up what she’s playing with, or else she won’t learn how to share.

They will undermine me and demand my daughter give the toy to my son whenever they are over.

I just don’t think that’s right. I’ve gotten into fights with them over this, bc I don’t like them coming here and telling me what to do, and also I feel like this will make my daughter think she has to give up whatever she is playing with to make my son happy, won’t that make her a pushover?