Is this sentence OK?
(two people, two things etc.)

There is a resemblance between them.

Question

Is this sentence OK?
(two people, two things etc.)

There is a resemblance between them.

Answer

Yes. That sentence is correct. For instance....

Mark: Doesn't she look like Angelina Jolie? 
Dan: Yes, there is a resemblance between them.

Answer

Your sentence is OK. You can also say:
They resemble each other.

Answer

You need to provide more information for an answer. Maybe someone else can divine what you mean.
Oh. now I see. Yes, you're correct.