Can I have my children's last name changed to mine.

Yes.
I don't really know how to do it but I know you can change the last name.
Xox

Hi, advocatem!

Generally, it is possible, but sometimes not.

There are a number of unknown factors here. For instance, why you are wanting to change their last names, where the other, natural parent is and the relationship that the other parent presently has with the children, the age of the children, the laws concerning this where you are located, etc.

If you would provide some additional details, it would be easier for people to help you here.

Thanks!