Would you put sun-in in your toddler’s hair?

So my SIL and I both have girls that just turned two. My daughter has lighter hair than her daughter, and she’s always made it known that she wishes her daughter had lighter hair (she also feels the need to have everything that I have and copy everything single thing that I do/buy and not only that, but one-up it). Anyway, she asked me if I put sun-in in my daughters hair because she has really natural blonde highlights with a little bit of a reddish tint. So I saw her a couple weeks later and both her kids hair is SUPER blonde and reddish, it was sooo obvious that she put sun-in in their hair. I think it’s pretty selfish to put those damaging chemicals in their hair and when they’re so little, just to please herself. Not something I would do but to each their own. I’m just curious- What are your opinions on it?