I don't want anyone to feel a way

I've been with this guy for almost a year and he has a daughter about 4 or 5. He has her like 3 days of the week or more but her hair is never comb most of the time and it bothers me and I'm not sure how to tell my boyfriend about it without it being a argument. I would would comb it for her but I'm not sure how her parent would react. 🤷. Her mom's hair always on flick but just don't the child.