Resolved Question

People who are very much involved in each other are they anyway related in their last birth? If yes, is there any way to find out or get some hint?

It is likely that they were in some way related in their past-lives.

We usually embody with a group of other souls with whom we have had some - perhaps many - lives together, in various relationships, family or friendly. They are our "soul-group"; they are often people who in this life we recognise when we come across them, as someone we've "met before" and are in tune with.

It is possible to find this out; a competent psychic can look up the Akashic Records ("Records of Nature"), or if you've a mind, you can develop the ability to use a pendulum and ask your spiritual guidance what the past relationship was with someone. You may or may not be given an answer - only if it is thought useful for you to know.
I had a school friend whom I was very fond of, and he of me; but a bit later in life when I consulted with a psychic, I asked what our past association had been, and I was told that I didn't have permission to know! So that was that... I had to accept that as wisdom.