I quit my job in Nov 2015 and now planning to re-join the company. I appeared for few interviews over the phone and they enquire about this gap which i was unable to answer effectively. What should be the proper answer for this? My reason to leave the company was my family issues. Will they consider it or it will be a weak point to mention.
Honesty is usually the best policy.
Simply state that you had a break from work to deal with family issues which are now resolved. There's no harm in implying that these were health issues, which reinforces your caring/commitment personality.
As long as you demonstrate that you're in a fit state to work, I don't think the gap will be much of a problem.
My reason to leave the company was my family issues. Will they consider it or it will be a weak point to mention.
If your reply is just the one sentence "I quit because of family issues", then it will certainly be a weak point. Without more information, the company will be free to imagine all sorts of things, and will certainly wonder if you will quit because of family issues again in the near future.
Many companies like to have employees who value working and value their job. Abruptly quitting and not working at all, without important reasons for doing so, may indeed appear as a weak point.
Instead during your interview elaborate a bit about the family issues. You don't need to go into a lot of detail, but it would make sense to explain what kind of family issue needed your attention so much that you could not work at all.
If it's reasonable you also want to reassure the company that the family issues are resolved and behind you now, and that you don't see them recurring in the foreseeable future.
A little bit more than "family issues" will go a long way here and will help stop this from being a weak point.