(Sa) inyo, yours, (to etc.) you (plural), and (sa) kanila, theirs, (to etc.) them, are used as the polite alternatives to (sa) iyo, yours, (to etc.) you (singular).
See also: Polite “you” (p. 45)
This grammar reference is part of the Learning Tagalog Course.
Learn Tagalog in a simple and fun way.
Try the course free
“I got a copy of your book and I love it. It’s really the best I’ve come across.”
— Martin Kelemenis, Geneva, Switzerland