I'm supposing these are cousins or very close family friends - they spent many Christmases together in the 1950s / early 1960s.
They are so cute!

The kneeling girl in the red jumper and the seated girl in front of her appear in many of the slides I acquired. It's possible their names are Nancy and Patty (based on some Christmas gifts in other slides) - I will refer to them as Nancy and Patty in the below slides. The red-headed boy is also easy to pick out in these slides.

Nancy and Patty are back/right and the girl behind the doll.

Nancy and Patty are standing in the center and seated on the right.

Nancy and Patty are standing on the right.

Nancy and Patty are standing in the back row left and standing in the middle row right.

This is the same year - the girl with the green skirt marries the young man in the center back according to some other slides from this large lot.

Sadly this is a poor slide but the cousins now include the next generation so I really wanted to include it. Nancy and Patty are wearing a blue blouse and a red blouse (I think). This slide was labeled 1962.
Do you recognize anyone in these slides?