Hello, 

First of all, a big thanks to the whole forum. I benefitted a lot from all the experiences shared here.
Now, I am stuck with something and could not find a solution to it.

I am planning to invite my parents to Germany and I have obtained the verpflichtungserklärung already. I read a lot of posts and I understand having a formal obligation makes their case strong but in my case, my father only works for a family member and does not have too much to show in terms of his finance. 
Will that be a problem? If yes, what are the options/alternatives for this? 
If any of you faced this issue before, kindly share some suggestions.